A preliminary biological assessment of Kirwin National Wildlife Refuge

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A Preliminary Biological
Assessment of Kirwin
National Wildlife Refuge
Biological Technical Publication
BTP-R6004-2004
U.S. Fish & Wildlife Service
A Preliminary Biological Assestment of Kirwin
National Wildlife Refuge
Biological Technical Publication
BTP-R6004-2004
Murray K. Laubhan
U.S. Geological Survey, Northern Prairie Wildlife Research Center
8711 37th Street SE, Jamestown, North Dakota, USA 58401
U.S. Fish & Wildlife Service
Author Contact information:
Murray K. Laubhan, U.S. Geological Survey,
Northern Prairie Wildlife Research Center, 8711 37th
St. SE, Jamestown, ND 58401.
Phone: 701/ 253 5534,
Fax: 701/ 253 5553
Email: murray_laubhan@usgs.gov.
For additional copies or information, contact:
Wayne J. King, USFWS Region 6, Regional Refuge
Biologist. P.O. Box 25486 Denver Federal Center
Denver, Colorado 80225-0486
Phone: 303/236 8102
Fax: 303/236 4792
Email: wayne_j_king@fws.gov
Recommended citation:
Laubhan, M. K. 2004. A preliminary biological
assessment of Kirwin National Wildlife Refuge,
Phillipsburg, Kansas. U.S. Department of Interior,
Fish and Wildlife Service, Biological Technical
Publication, BTP-R6004-2004, Washington, D.C.
Series Senior Technical Editor:
Stephanie L. Jones, USFWS, Region 6 , Nongame
Migratory Bird Coordinator, P.O. Box 25486 Denver
Federal Center Denver, Colorado 80225-0486
Associate Editor:
Wayne J. King, Regional Refuge Biologist USFWS,
Region 6, P.O. Box 25486, Denver Federal Center,
Denver, Colorado 80225-0486
Table of Contents
Summary .......................................................................................................................................................... 1
Acknowledgments ........................................................................................................................................... 2
Introduction ..................................................................................................................................................... 3
Description ....................................................................................................................................................... 4
Refuge Establishment and Authorities .......................................................................................... 4
Location and Topography ................................................................................................................. 4
Climate .............................................................................................................................................. 5
Geology .............................................................................................................................................. 5
Groundwater ..................................................................................................................................... 6
Soils ................................................................................................................................................... 6
Vegetation ......................................................................................................................................... 6
Wildlife Conservation ...................................................................................................................................... 8
Kirwin National Wildlife Refuge ...................................................................................................... 8
State of Kansas ................................................................................................................................. 8
Bird Conservation Region ................................................................................................................. 9
Birds of Conservation Concern ........................................................................................................ 9
North American Waterfowl Management Plan ............................................................................. 9
Partner’s In Flight North American Landbird Conservation Plan............................................10
Shorebird Conservation Region ......................................................................................................10
Waterbird Conservation Region .....................................................................................................10
Playa Lakes Joint Venture ..............................................................................................................10
Community Types ..........................................................................................................................................11
Reservoir (Deepwater) ....................................................................................................................11
Managment Potential ....................................................................................................................13
Shoreline ..........................................................................................................................................13
Managment Potential .....................................................................................................................15
Riparian ............................................................................................................................................15
Managment Potential .....................................................................................................................18
Upland ..............................................................................................................................................19
Managment Potential .....................................................................................................................21
Public Use .......................................................................................................................................................22
Literature Cited ..............................................................................................................................................23
Appendix A. Potential information needs that may be required to address the recommendations
provided in the evaluation section ..................................................................................................................27
Appendix B. Scientific and common names of animals and plants known to occur on Kirwin NWR.
Information on fish, amphibians, and reptiles obtained from Kansas Department of Wildlife and
Parks (refuge files dated 01/30/2003) ..............................................................................................................29
Appendix C. Total annual use days, average annual populations, and peak populations, respectively
for the following waterfowl groups using Kirwin National Wildlife Refuge between 1983 and 2001:
American Coot and dabbling ducks excluding Mallard (a – c), diving ducks (d – f), Canada Goose
and Mallard (g – i), and White-fronted Goose and Snow Goose (j – k). .......................................................33
Appendix D. Conservation status for avian species based on regional and national plans ...................... 39
1
Summary
This report represents an initial biological
assessment of Kirwin National Wildlife Refuge
(NWR) conducted as part of the pre-planning phase
for development of a Comprehensive Conservation
Plan (CCP). Stimulation for the report was based on
the concept that future decisions related to the
biological portion of the CCP will be based on the best
available science. Therefore, an attempt is made to
integrate information from many different scientific
disciplines (e.g., geology, hydrology, biology) to help
identify ecological constraints and opportunities
imposed by the land base being considered.
Consequently, there is a greater likelihood of
identifying potential shortcomings of various
management actions during the decision making
process.
Information in this report is based on a relatively
limited number of published articles, past notes, and
observations. An attempt was made to locate
sufficient relevant information necessary to formulate
more definitive ideas and provide additional context.
Thus, the information provided below is known to be
incomplete and a more thorough synthesis will be
required. Further, interpretation of published
information can vary among individuals and the refuge
staff is encouraged to review the documents cited in
this report. Their years of observation and experience
managing the refuge are invaluable to ensuring that
information used to make decisions is applicable.
Consequently, some sections contain information that
was not fully explored in the evaluation section;
however, it was retained because it may be useful as
the refuge staff and core CCP team examines
different management options. Finally, decisions
regarding management of each individual community
should be combined and evaluated collectively to
identify potential conflicts. Although this may seem
simple and straightforward, this task often is difficult
because it frequently requires an iterative approach to
ensure that important issues have not been omitted.
This report does not contain conclusions, nor does it
advocate any opinions (favorable or unfavorable)
regarding the biological program. Further, concepts
such as alternatives, goals, and objectives, are not
discussed. The core CCP team will address these
topics. Rather, it represents a summary that
hopefully will be used to focus future discussion
regarding biological data needs and approaches for
using this information to make decisions. Ultimately,
however, scientific information alone will not lead to a
definitive decision regarding future direction, because
biology is only one of many components that must be
considered in the evaluation. Therefore, it is
recommended that U. S. Fish and Wildlife Service
(FWS) personnel responsible for determining the
future direction of the refuge be consulted to establish
guidelines and agree on the approach that will be used
in evaluating the biological program prior to
proceeding.
2
Acknowledgments
Prior to writing the report, the author was invited to
the refuge for a two-day meeting with Erich Gilbert
(refuge manager), Craig Mowry (assistant refuge
manager), and Wayne King (regional refuge biologist).
The purpose was to become familiar with the site,
discuss management opportunities and constraints,
and identify potential types of information that would
assist the staff in developing a credible biological plan
to guide future management. These individuals
contributed significant time and insight regarding
management of the refuge. The assistance of Rachel
Lambhan and Mark Fly in locating and processing
information used in this report is greatly appreciated.
Thanks also to the following individuals for providing
reviews of an earlier draft: E. Gilbert, R. A. Gleason,
S. L. Jones, W. J. King, R.A. Laubhan, C. Mowry, D.
M. Mushet, and J. D. Petty.
3
Introduction
Stimulation for this report was generated by passage
of the 1997 National Wildlife Refuge System
Improvement Act (NWRSIA) that requires each
refuge in the National Wildlife Refuge System to
develop a CCP that includes goals and objectives that
are based on the best available science. To accomplish
this mandate, Region 6 of FWS contracted with the
Biological Resources Division of the U. S. Geological
Survey (USGS) to inspect refuge habitats and
synthesize available information pertinent to the
management of Kirwin NWR as part of a pre-planning
phase to guide development of a CCP. This report
represents such a synthesis.
The brevity of the site visit did not allow for detailed
discussions between USGS and FWS personnel, but it
did provide the opportunity to exchange thoughts
regarding the information needed to evaluate the
biological program. Thus, the ideas contained within
this report are of a general nature and should be
viewed as a collaborative effort that involved the
refuge staff. Additional work will be required to
objectively evaluate the biological program, and this
report should be viewed as an initial effort to start this
process. In addition, there are alternative ways of
approaching an evaluation that would require different
levels and types of information. Therefore, the
responsibility of FWS is to review the report and
other relevant materials, discuss available options
with appropriate personnel, and determine if the
identified information needs and recommendations
outlined in this report are acceptable and represent
the preferred manner of proceeding.
General descriptive information on refuge
establishment, topography, climate, geology, soils,
vegetation, and wildlife is intended to provide a brief
background of the refuge with regard to functions,
processes, and values. This information is important
as a baseline for understanding the impact of past
land alterations and for developing management
guidelines for the future. In contrast, the section on
conservation is intended to provide perspective
regarding potential refuge contributions to natural
resources based on conservation plans that have been
developed for application at larger geographic scales
that encompass the refuge. The section on evaluation
of community types discusses in more detail the
attributes of various communities that occur within
the refuge boundary. For ease of discussion, four
broad communities were delineated as follows: (1)
Reservoir Pool, (2) Shoreline, (3) Riparian, and (4)
Upland. For each community, a brief synopsis of
historic and current conditions is provided. Also,
potential management options are discussed along
with some associated benefits and detriments.
Appendix A summarizes the information needs that
may be required to address the recommendations
provided in the evaluation section. These
recommendations largely are those of the author and
are based on thoughts that resulted from discussions
with FWS personnel during the site visit trip in
March. Therefore, the list is incomplete from a
biological perspective and largely ignores recreational
and other considerations. Additional effort will be
required by FWS personnel to identify and integrate
issues, concerns, and recommendations through
internal discussions and public scoping. Although
some scoping has already occurred, hopefully this
report will assist future efforts by providing some
background biological information. Obviously, this
represents only the first step in a long process and
additional work is necessary.
4
Description
Refuge Establishment and Authorities
Kirwin NWR is an overlay project on a U. S. Bureau of
Reclamation (BOR) irrigation and flood control
reservoir known as Kirwin (U. S. Fish and Wildlife
Service, URL http://kirwin.fws.gov/refugemap.htm).
The reservoir was constructed before irrigation
became widely practiced (Christensen 1999).
Dedicated in 1955, the reservoir has a contributing
drainage area of 3,540 km2 (1,367 mi2) and a total water
storage capacity of 38,797 ha-m (314,550 ac-ft). The
storage capacity is allocated among flood control
(36.532 ha-m [215,115 ac-ft]), conservation storage
(11,057 ha-m [89,650 ac-ft]), and inactive or dead
storage (1,207 ha-m [9,785 ac-ft]) (Christensen 1999).
Kirwin NWR was established in 1954 pursuant to the
Fish and Wildlife Coordination Act (16 U.S.C. ¤ 664)
for the “…conservation, maintenance, and
management of wildlife, resources thereof, and its
habitat thereon,…” (U. S. Fish and Wildlife Service,
URL http://refuges.fws.gov/policymakers/). The
BOR owns the land and controls reservoir water
levels, whereas the refuge staff manages all other
activities on the land and water (U. S. Bureau of
Reclamation, URL http://www.usbr.gov/gp).
Location and Topography
The 4,366-ha (10,788 ac) refuge includes Kirwin
Reservoir and bordering areas in southeast Phillips
County, Kansas. Topography of the area is
characterized by rolling hills, the gently sloping
Kirwin terrace, and a narrow river valley formed by
the North Fork of the Solomon River (Leonard 1952,
Christensen 1999). The refuge encompasses portions
of the North Fork Solomon River and Bow Creek.
These rivers drain an area of 359,874 ha (889,248 ac)
above the reservoir (U.S. Bureau of Reclamation 2002).
The altitude of the terrace ranges from an elevation of
602 m (1,975 ft) in Phillips County to 445 m (1,460 ft) in
Mitchell County. The gradient of the North Fork
Solomon River channel is about 1.3 m/km (7.1 ft/mi) in
Phillips County.
The refuge is located in the North Fork Solomon
River Sub-Basin. The North Fork Solomon originates
in western Thomas County, Kansas, approximately
193 km (120 mi) west of Kirwin Dam and drains an
area of 3,556 km2 (1,373 mi2) (U.S. Bureau of
Reclamation 2002). Elevation of the area ranges from
about 430 m (1,410 ft) at the mouth of North Fork
Solomon River in Mitchell County, to about 640 m
(2,100 ft) in the western part of Phillips County. Like
other valleys in north-central Kansas, the North Fork
Solomon valley and its tributaries are asymmetrical
and typically have precipitous south walls and gently
sloping north walls. According to Leonard (1952) the
valley consists of broad undissected terraces and a
floodplain width that varies from 201-805 m (660-2,640
ft). The relief from the stream channel to the top of
the Kirwin terrace, which lies above flood level, is as
much as 12 m (40 ft). The Kirwin terrace slopes
gently (gradient = 1.4 m/km [7.3 ft/mile]), is
moderately well drained, and represents the primary
area of cultivated farmland. Historically, the elevation
of the floodplain varied between 4.6-7.6 m (15-25 ft)
below the Kirwin terrace and 3.7-4.9 m (12-16 ft) above
the water level of the river. Many of the ephemeral
streams that drain the uplands disappear on the
surface of the terrace, which suggests these streams
contribute a large part of their water to the
groundwater reservoir in the area.
Agriculture and ranching have been the primary
economic forces in the area since the early 1800’s (U.S.
Bureau of Reclamation 2002). In Phillips County, the
land in farms (220,398 ha [554,603 ac]) accounted for
97.8% of the county land base (229,478 ha [567,040 ac])
in 1997. Further, of the land in farms, cropland
(130,329 ha [322,043 ac]) accounted for 56.8% of the
county land base (U. S. Bureau of Reclamation 2002).
Representative crops produced in Phillips County
during 1997 included corn, sorghum, wheat, oats,
soybeans, and hay (U. S. Department of Agriculture
National Agricultural Statistics Services, URL http://
www.nass.usda.gov/census/census97/highlights/ks/
ksc074.txt).
The drainage area below the reservoir is 348,004 ha
(859,918 ac), of which 6,325 ha (1.8%; 15,630 ac) is
irrigated (Christensen 1999). The BOR operates
Kirwin Irrigation District Number 1 downstream
from the reservoir and provides surface water outflow
to irrigate as much as 4,650 ha (11,490 ac) of farmland
(U.S. Bureau of Reclamation 2002) that generally is
within 8 km (5 mi) of the North Fork Solomon River
(Christensen 1999). As mentioned previously, the
drainage area above the reservoir is 359,874 ha (889,248
ac), of which 24,525 ha (6.8%; 60,600 ac) is irrigated.
The use of surface water for irrigation first occurred
in 1928 with the establishment of two pumping plants,
but by 1946 a total 13 plants had been established
(Leonard 1952). Currently, the primary source of
irrigation water is from alluvial wells, which have
increased from <10 in 1949 to>150 in 1993 (U.S.
Bureau of Reclamation 2002).
The North Fork Solomon Sub-Basin is part of the
Solomon River Basin, which extends across parts of 17
Kansas counties and includes the Solomon River and
its major tributaries, the North Fork and South Fork
Solomon Rivers. The rivers and associated tributaries
drain approximately 17,716 km2 (6,840 mi2) of mainly
agricultural land (Christensen 1999). In addition to
Kirwin Reservoir, the BOR also operates two
additional reservoirs in the basin; Webster Reservoir
on the South Fork Solomon River and Waconda Lake
at the confluence of the North and South Fork
Solomon Rivers. The three reservoirs provide water
for irrigation, municipal, industrial, and domestic use;
flood control; recreation; and fish and wildlife habitat
(Christensen 1999).
The elevation of the basin varies from approximately
1,006 m (3,300 ft) in the west to 351 m (1,150 ft) in the
east near the town of Solomon, Kansas. The average
gradient of the region is approximately 2.7-2.8 m/km
(14-15 ft/mi). The average gradient for the main stem
123°
5
Solomon River is 0.9 m/km (5 ft/mi) (U.S. Bureau of
Reclamation 2002). Both the North Fork and South
Fork Solomon Rivers derive their flows from
precipitation runoff and groundwater discharge from
underlying aquifers (U.S. Bureau of Reclamation
2002).
Finally, the Solomon River Basin is located in both the
Smoky Hills and High Plains Physiographic Regions
of the Great Plains Physiographic Province
(Launchbaugh and Owensby 1978). The High Plains
region of Kansas extends from the western state line
eastward into Graham County. The topography is
characterized by flat to gently rolling hills with
narrow, shallow valleys of low relief. Sand, gravel, and
porous rock cover most of the region. The Smoky
Hills Region, which encompasses Kirwin NWR, is
composed of three distinct hill ranges. Steep chalk
bluffs characterize the western range of hills, whereas
Greenhorn Limestone and Dakota Sandstone cap the
middle and eastern range of hills, respectively. The
eastern boundary of the Smoky Hills Region is in Clay
County and is adjacent to the Flint Hills
Physiographic Region (Kansas Geological Survey,
URL http://www.kgs.ukans.edu/Physio/physio.html).
Vegetation communities within this region are
classified as mixed-grass prairie with forested river
bottoms (Kuchler 1974).
Climate
The climate of the Solomon Basin is classified as
subhumid. Summers are characterized by hot days
and cool evenings, whereas winters are normally
moderate with light snowfall and only occasional short
periods of severe cold. The average length of the
growing season is about 167 days (Leonard 1952) and
the frost-free period extends from 29 April to 13
October (Albertson 1937). Long-term climate data (5/
1/1952 – 12/31/2002) was obtained from the National
Climate Data Center cooperative station located at
Kirwin Dam (http://lwf.ncdc.noaa.gov/oa/climate/,
station # 144357). The mean monthly maximum
temperature ranged from 3.1 C(37.5°F) in January to
33.4°C (92.2°F) in July, whereas mean monthly
minimum temperature ranged from -11.3°C (11.6°F) in
January to 17.8 °C (64.0°F) in July.
Average annual precipitation during this period was
58.5 cm (23.0 in), with 44.2% of total annual
precipitation occurring in May (mean = 10.2 cm [4.0
in]), June (mean = 7.8 cm [3.1 in]), and July (mean =
7.7 cm [3.0 in]). However, not all of this moisture is
necessarily available for plant growth because
evaporation is also occurring during these months.
Graphs obtained from the National Oceanic and
Atmospheric Administration (URL http://
www.noaa.gov), which depict ranges of evaporation for
the entire U.S, were used to obtain a coarse estimate
of 28.2 cm (11.1 in) of annual evaporation for north-central
Kansas. Months with highest evaporative
losses were June (5.6 cm [2.2 in]), July (6.1 cm [2.4 in]),
and August (5.6 cm [2.2 in]).
The Palmer Drought Severity Index (PDSI) was
developed to represent the severity of dry and wet
periods based on monthly temperature and
precipitation data as well as the water holding
capacity of soils at a location (Palmer 1965). Thus, this
measure provides a method integrating the above
information. For north-central Kansas, the long-term
PDSI (1895-2002) indicates cyclic patterns of drought
and wetness. During 1989 and 1990, portions of 1991,
and for a brief period in 2001, this region experienced
severe drought, but from late 1993 through mid-1994
the area was extremely wet (National Climate Data
Center, URL http://lwf.ncdc.noaa.gov/oa/climate/).
Geology
The surface geology of the Solomon Basin consists of
unconsolidated and consolidated rocks. The
unconsolidated surface deposits consist of Quaternary
alluvium, loess, and the Tertiary Ogallala Formation,
whereas Cretaceous and Permian rocks form the
bedrock. In general, the basin is underlain by strata
of marine origin (Christensen 1999). The dendritic and
asymmetrical drainage pattern of the Solomon River
suggests the lack of faults and folds and the presence
of flat underlying rock units (U.S. Bureau of
Reclamation 1984).
The Greenhorn Limestone, Graneros Shale, and
Dakota Sandstone outcrop as far east as western Clay
County, Kansas. Permian beds outcrop in counties
farther east. The Greenhorn Limestone consists of
alternating beds of calcareous shale and chalky
limestone. The Graneros Shale is noncalcareous,
fissile shale with sandstone lenses. The Dakota
Formation consists of lenticular sandstone bodies that
are embedded in mudstone. Generally, the sandstones
are fine to medium grained, well sorted, and exhibit
cross-bedding (Kansas Department of Agriculture
Division of Water Resources), URL http://
www.accesskansas.org/kda/dwr/).
The North Fork Solomon River is underlain by, or
incised into, Cretaceous beds that generally dip to the
west, whereas the erosional surface generally slopes
to the east. The oldest subsurface rocks at the
eastern end of the basin are of the Sumner Group.
Above the Sumner Group is Cretaceous marine
sediment beginning with the Dakota Formation, which
is overlain by the Cheyenne Sandstone, Kiowa Shale,
Graneros Shale, Greenhorn Limestone, and Carlile
Shale. The Carlile Shale is exposed in stream valleys
in Phillips County. Above the Carlile Shale is the
Niobrara Formation, which is exposed in much of the
North Fork Solomon River Basin (Leonard 1952), and
the Pierre shale, of which there is only one known
small outcrop in the basin upstream from Webster
Reservoir (Moore and Landes 1937, Ross 1991). The
Pierre Shale lies conformably on the Niobrara Chalk,
which is a gray, shaly, fossiliferous chalk with
weathered surfaces. The chalk contains bentonite
beds and limonite concretions (Kansas Department of
Agriculture Division of Water Resources).
The north and south divides of the Solomon River are
capped by remnants of the Ogallala formation in the
western part of the Solomon Basin, whereas the
uplands and valley walls over much of north-central
6
Kansas are composed of loess of the Sanborn
formation that was deposited during glacial retreat
(Leonard 1952). The Ogallala formation was formed
during the Pliocene by eastward flowing streams that
filled pre-existing valleys with alluvial sediments.
Continued deposition of alluvial sediments formed a
broad alluvial plain. The Ogallala consists mainly of
silt, sand, gravel, and “mortar beds” formed by
cementation of sediments with calcium carbonate.
However, lenticular beds of well-sorted sand, gravel,
bentonite, and volcanic ash also exist. The Ogallala
lies unconformably on the Pierre Shale in the western
part of the basin and on the Niobrara Formation in the
eastern part of the basin. The surface of the Ogallala
dips to the east-northeast and the average gradient is
2.1 m/km (11 ft/mi) (Kansas Department of
Agriculture Division of Water Resources).
Narrow belts of alluvium, most of Recent age, are
adjacent to the Solomon River channel and its
tributaries and occupy the floodplain (Leonard 1952).
The alluvium consists mainly of gravel, sand, silt, and
some clay. However, loess also may occur along
major streams. The loess is underlain by stream-deposited
sands that are in a high terrace position
with respect to the valleys (Leonard 1952). At several
places in the floodplain, wind has deposited sand from
the alluvium into dunes or in thin layers that cover the
terrace surfaces (Leonard 1952). These areas of sand
deposition occur in Phillips County, but thickness of
the fluvial and loess deposits is < 3.0 m (10 ft) (Kansas
Department of Agriculture Division of Water
Resources). A map illustrating the locations of these
geologic features on the refuge was developed by
Johnson and Arbogast (1993) and can be obtained from
the Kansas Geological Survey (URL http://
www.kgs.ukans.edu/General/Geology/County/nop/
phillips.html).
Groundwater
The Sanborn formation, which consists of a thin layer
of loess that overlies Cretaceous rocks, is a locally
important source of groundwater (Leonard 1952). The
most important aquifer in the area, however, occurs in
the deposits underlying the Kirwin terrace surface.
In general, this terrace is underlain by 9.1-27.4 m (30-
90 ft) of unconsolidated deposits (e.g., coarse textured
sand and gravel) that is quite permeable and lies
below the water table (Leonard 1952). The broad,
nearly flat terrace surface constitutes a large
recharge area and streams that originate in nearby
hills contribute additional recharge. Groundwater
moves laterally through the terrace deposits and into
the alluvium or into the channel of North Fork
Solomon River. Thus, the water table in the Recent
alluvium is continuous with the water table in the
terrace deposits and with the water level in the
flowing streams. The coarse nature of the alluvium
makes it an important potential source of
groundwater (Leonard 1952). Hydraulic conductivity
has been estimated at 51.8 m/day (170 ft/day) with an
average transmissivity of 241.5 m2/day (2,600 ft2/day)
(Phillips 1980). Well yields vary from 38-1893 l/min
(10-500 gal/min).
The water table in the valley slopes from east to west,
and from the sides of the valley toward the center.
The downstream slope of the water table varies from
about 2.2 m/km (11.5 ft/mi) in western Phillips County
to about 1.2 m/km (6.4 ft/mi) near the town of Kirwin
(Leonard 1952). Most ephemeral streams in the area
are above the water table and, when flowing, probably
contribute some water to the groundwater. In
contrast, the Solomon River and Bow Creek are
gaining streams (e.g., flow in these streams is
partially maintained by groundwater that seeps into
the channel) (Leonard 1952).
Soils
In north-central Kansas, soils are composed primarily
of Mollisols in the suborder Ustolls. A dark surface
horizon rich in bases are primary characteristics of
Mollisols. Nearly all have a mollic epipedon, but
many also have an argillic, nitric, or calcic horizon.
Specifically, soils of the North Solomon Valley are
primarily fertile, silty clay loams derived from
reworked loess (Leonard 1952), some of which are rich
in selenium (U. S. Geological Survey, URL http://
ks.water.usgs.gov/Kansas/studies/ressed/). The soils
in valleys are slightly sloping, friable, and generally
have high agricultural productivity. In the western
and central parts of the basin, soils are generally
friable and relatively impermeable, with some silt
loam and loess. The more level soils in the western
and central parts of the basin are used for grain
cultivation and are moderately productive. The soils
in the eastern part of the basin range from shallow
sands to thick clays and generally have low
agricultural productivity (U.S. Bureau of Reclamation
1984).
Vegetation
Historically, the floodplains of both rivers supported
woody vegetation, tall grasses, and forbs, whereas the
uplands largely were mixed-grass prairie (Kuchler
1974). However, human settlement and associated
land use activities altered historic processes and,
ultimately, the plant and wildlife communities.
Although construction of the reservoir in 1952
represents an obvious perturbation that altered
various ecological aspects of the rivers and associated
floodplains, alteration of the uplands also occurred
prior to refuge establishment. The area surrounding
Kirwin NWR was cultivated extensively and also was
used to pasture cattle prior to 1945 (Leonard 1952).
The general location of these activities was related to
topography and soils. Much of the cultivation
occurred on the terrace due to the presence of fertile,
moderately well drained soils. In contrast, cattle
production typically occurred on areas bordering the
valley where cultivation was prevented because of
steep gradients or presence of rocky soil formed on
chalk and limestone rocks (Leonard 1952). Although a
detailed history of past land use was not developed for
the refuge, a study conducted by Rezsutek (1990)
supports this scenario. He reports that lands
composing the refuge were formerly family farms and
much of the native grassland in the area had been
turned under for the production of crops prior to
establishment. Further, although J. Launchbaugh (in
7
K. Launchbaugh’s field notes) described some areas
as “native prairie”, Rezsutek (1990) suggests they
may have been “restored prairie”.
Grassland, cropland, deepwater and shoreline habitats
of the reservoir, and riparian zones bordering the
tributary rivers are dominant communities on the
refuge. In addition, shelterbelts, palustrine wetlands,
and chalk bluffs also occur within the refuge
boundary. When the reservoir is at conservation pool
(527.1 m [1729.25 ft]) there are 2,050 ha (5,065 ac) of
surface water and about 60 km (37 mi) of shoreline.
According to refuge staff, croplands occupy about 486
ha (1,200 ac) at conservation pool. Remaining
community types encompass 1,826 ha (4,513 ac) at
conservation pool and include grasslands,
shelterbelts, and riparian habitat. However, the area
of each community was not available.
Of the community types on the refuge, the reservoir
(e.g., deepwater habitat) and associated shoreline,
cropland, and shelterbelts were not present prior to
human settlement. Consequently, the area of native
communities on the refuge has been reduced.
Further, the grassland and riparian communities,
although historically present, have been severely
altered floristically and structurally. For example,
two plant species that may occur on the refuge
(western prairie-fringed orchid and Meads milkweed;
scientific names of all species mentioned in this report
are given in Appendix B) are listed as threatened or
endangered under the Endangered Species Act (ESA)
of 1973 (16 U.S.C. 1531-1544, 87 Stat. 884; URL: http://
laws.fws.gov/lawsdigest/esact.html). More detailed
information is presented in the section entitled
Evaluation of Community Types.
8
The 1997 NWRSIA mandates that each refuge
develop a CCP that is consistent with the principles of
sound fish and wildlife management and available
science. Further, this act also specifies that each CCP
shall identify and describe the purposes of each
refuge; the distribution, migration patterns, and
abundance of fish, wildlife, and plant populations and
related habitats; significant problems that may
adversely affect the populations and habitats of fish,
wildlife, and plants and the actions necessary to
correct or mitigate such problems; and, to the
maximum extent practicable and consistent with this
Act, be consistent with fish and wildlife conservation
plans of the State in which the refuge is located.
The purpose of this report was not to fully develop
information on all species potentially occurring on the
refuge. However, some general future direction must
be specified with regard to wildlife given the purpose
for refuge establishment. Therefore, this report
concentrates on the importance of the refuge to
migratory birds because these species represent a
primary FWS responsibility according to the
requirements of the Migratory Bird Treaty Act of
1918 (16 USC 703-711; 40 Stat. 755; URL: http://
laws.fws.gov/lawsdigest/migtrea.html). This should
not be interpreted as meaning other vertebrates,
invertebrates (e.g., butterflies), and plants can be
ignored since these organisms are important as
individual entities and also because they are critical to
proper system function. Rather, information
regarding the habitat requirements of these species
also should be used in evaluating the direction of
future refuge management to ensure that valuable
opportunities are not overlooked.
Baseline information on the avian community of
Kirwin NWR was developed using a checklist of bird
species sighted on the refuge (Igl 1996). Scientific
names for all species mentioned are provided in
Appendix B; birds follow the American Ornithologists’
Union Committee on Classification and Nomenclature
(American Ornithologists’ Union 1998, 2000, 2002,
2003). In addition, refuge files of duck, goose, and
swan counts were used to generate graphs of total
annual use days, average annual populations, and
average peak populations spanning a 20-year period
(Appendix C). There are several qualifying factors
that must be considered when considering this
information. First, the list from the website
represents a composite of all birds that have been
sighted over a long time; thus, the list may not
accurately represent the current avian community.
Second, the list only designates occurrence; thus, the
contribution (e.g., source/sink) of the refuge to the
species population is not known. Although refuge
waterfowl counts contribute information on
abundance, it is difficult to compare data among years
with any certainty because routes and areas surveyed
are not available and likely have varied among years.
In addition, count information was not collected based
on community type or bird activity. Thus, it was not
possible to use this information to determine local use
patterns or assess relative importance of different
communities. Similarly, the avian list (Appendix B)
was not developed using standardized protocols and
methods, but based on the long-term refuge bird list,
with an additional 29 species added from a research
study conducted in the riparian zone on the refuge in
the mid-1990s (Sevigny 1998). Regardless of these
constraints, this list is valuable because it can help
focus discussion among individuals (e.g., FWS
personnel, core CCP team) responsible for
determining the future management direction of the
refuge.
Finally, depending on the source and type of
information sought, Kirwin NWR is located in many
different regions. In all cases, there is considerable
overlap among boundaries although the area
encompassed tends to vary greatly. To provide an
overall perspective, relevant information regarding
species of concern and population targets contained in
these plans has been summarized, but no attempt has
been made to prioritize or make decisions regarding
species or guilds that should receive attention. In
some cases, species considered to be of conservation
concern at a regional level may not be of concern at a
national level, or vice versa. Such differences do not
indicate discrepancies; rather, it suggests differences
in distribution and population status at different
geographical scales. However, the small size of the
refuge precludes providing quality habitat for all
species and decisions likely will be required to
evaluate tradeoffs in management approaches and for
development of detailed habitat objectives.
Kirwin National Wildlife Refuge
The refuge bird list includes 233 species, of which 45
are recorded as nesting and four (Piping Plover, Bald
Eagle, Whooping Crane, and Least Tern) are listed as
threatened or endangered under the ESA. Kirwin
NWR also is recognized as a globally Important Bird
Area (IBA) by the American Bird Conservancy (URL
http://www.abcbirds.org/iba/kansas.htm). The IBA
program, initiated by BirdLife International in
Europe during the mid-1980’s, was developed to
recognize and support sites of importance to birds.
Based on the criteria developed by BirdLife
International, an IBA must maintain and support one
or more of the following: (1) species of concern (e.g.,
threatened and endangered), (2) species with
restricted ranges, (3) species vulnerable because of
population concentration, and (4) species vulnerable
because they occur at high densities due to their
congregative behavior (Kushlan et al. 2002).
State of Kansas
Wildlife resources in the state of Kansas were
historically rich and varied. Circa 1865, it is estimated
that the Great Plains portion of Kansas supported as
many as 407 bird species, including about 178 breeding
species (Fleharty 1995). Fish and herpetofauna were
not as rich due to the paucity of water, but included 30
fish species, 13 amphibian species, and 46 species of
reptiles (Fleharty 1995). Although Kirwin NWR is
small relative to the geographic area of Kansas, the
historic communities composing the refuge likely
supported many species mentioned in earlier
Wildlife Conservation
9
accounts. Appendix B contains a list of animals and
plants known to occur on the refuge.
Bird Conservation Region
Kirwin NWR is located within the Central Mixed-grass
Prairie Bird Conservation Region (BCR 19), an
ecologically distinct region of 535,734 km2 (206,848 mi2)
with similar bird communities, habitats, and resource
management issues. The area encompassed by BCR
19 extends from the edge of shortgrass prairie on the
west to the beginning of tallgrass prairie to the east
and includes portions of Texas, Oklahoma, Kansas,
and Nebraska (North American Bird Conservation
Initiative, URL http://www.nabci-us.org/map.html).
Although large areas in this region have been
converted to agriculture, areas of high-quality
grassland (e.g., Nebraska Sandhills) still remain,
including some of the best habitat for the Greater
Prairie-Chicken and Henslow’s Sparrow, and
sandbars along the larger rivers host a large
percentage of the continent’s breeding Least Tern
population. The region also is a spring migration area
for the American Avocet, Semipalmated Sandpiper,
and Buff-breasted Sandpiper.
Birds of Conservation Concern
The Birds of Conservation Concern (BCC) is the most
recent effort to satisfy the 1988 amendment to the
Fish and Wildlife Conservation Act, which mandates
FWS to “identify species, subspecies, and populations
of all migratory nongame birds that, without
additional conservation actions, are likely to become
candidates for listing under the Endangered Species
Act of 1973” (U. S. Fish and Wildlife Service 2002).
The document provides species lists at three
geographic scales: national, FWS regions, and BCRs.
Species considered for inclusion include nongame
birds, game birds without hunting seasons, and
numerous categories (candidate, proposed endangered
or threatened, and recently delisted) used in the ESA.
Parameters considered in determining if species
within these categories are of concern include
population size, extent of range, threats to habitat,
and other factors. The BCC should be consulted for
details regarding the assessment process.
There are 28 species known to occur on Kirwin NWR
that are considered to be of national conservation
concern in the BCC (U. S. Fish and Wildlife Service
2002). Among these are 8 shorebirds, 5 hawks and
falcons, 2 owls, and 2 sparrows. Twenty-one of these
28 species also are considered to be of conservation
concern at either FWS Region 6 or BCR 19 scale
(Appendix D). Special note should be made that some
species of conservation concern listed for BCR 19 are
not on the regional list and, likewise, several species of
regional conservation concern were not included in the
BCC list for BCR 19 (Appendix D).
North American Waterfowl Management Plan
The national goals set forth in the 1998 update of
North American Waterfowl Management Plan
(NAWMP) includes (1) maintaining the diversity of
duck species throughout North America and achieving
a mid-continent breeding population of 39 million
ducks during years with average environmental
conditions, and (2) reaching or exceeding mid-continent
populations for ten individual species,
including Gadwall, American Wigeon, Mallard, Blue-winged
and Cinnamon Teal, Northern Shoveler,
Northern Pintail, Green-winged Teal, Canvasback,
Redhead, and Greater and Lesser scaup. These
target populations are presented in Appendix D. The
plan also establishes population objectives for 30
populations of six goose species, three populations of
Trumpeter Swans, and two populations of Tundra
Swans. Of these, relevant objectives applicable to
Kirwin NWR include reducing all five populations of
Canada Geese that migrate through the central
flyway and also reducing mid-continent populations of
the Snow and Greater White-fronted geese to 1,000,000
and 600,000, respectively. The plan also sets forth
objectives to increase the interior population of
Trumpeter Swans to 2,500 and reduce the eastern
population of Tundra Swans to 80,000 (Appendix D).
Partner’s In Flight North American Landbird
Conservation Plan
The North American Landbird Conservation Plan
(NALCP) is a synthesis of priorities to guide national
and international conservation actions targeting 448
native landbirds from 45 families that breed in the
United States and Canada (Rich et al. 2004). Each
species is assigned scores ranging from 1 (low
vulnerability) to 5 (high vulnerability) for 6 factors
(population size, breeding distribution, nonbreeding
distribution, threats to breeding, threats to
nonbreeding, and population trend). These scores
subsequently are used to calculate a combined score
that represents relative conservation importance
(range = 4 [low concern] to 20 [high concern]).
Species with a combined score > 14, or combined
score = 13 and population trend score = 5, are
assigned to the Watch List that includes species of
highest conservation concern. In addition, a
Stewardship List was developed based on avifaunal
biomes in North America. These biomes were
delineated using cluster analyses to identify groups of
BCRs that share similar avifaunas. For each biome,
Stewardship Species are those species that have a
proportionately high percentage of their world
population within a single region during either the
breeding or wintering season. Kirwin NWR occurs in
the Prairie Avifaunal Biome, which is composed of
BCRs 11, 17-19, and 21-23 (Rich et al. 2004). The
NALCP should be consulted for details on the scoring
and assignment process, national and regional
population objectives, and other pertinent information
(Rich et al. 2004, URL http://
www.partnersinflight.org, URL http://www.rmbo.org/
pif/pifdb.html).
The Watch List and Stewardship List of continentally
important species in the United States and Canada
currently include 100 and 158 species (66 of these
species also occur on the Watch List), respectively
(Rich et al. 2004). Of these species, two (Greater
Prairie-Chicken, Dickcissel) of the Watch List species
and five (Mississippi Kite, American Tree Sparrow,
Lark Bunting, Grasshopper Sparrow, and Chestnut-
10
the Prairie Avifaunal Biome, respectively. Of these,
two species (Greater Prairie-Chicken and Dickcissel)
on the Watch List and six species (Mississippi Kite,
American Tree Sparrow, Lark Bunting, Grasshopper
Sparrow, Chestnut-collared Longspur, and Lapland
Longspur) on the Stewardship List are known to
occur on Kirwin NWR.
Shorebird Conservation Region
Kirwin NWR is located in the Central Plains/Playa
Lakes Region (CP/PLR) (United States Shorebird
Conservation Plan, URL http://
shorebirdplan.fws.gov/RegionalShorebird/
RegionsMap.asp). This region is larger than the area
encompassed by BCR 19 and includes portions of
Texas, eastern New Mexico and Colorado, western
Oklahoma, Kansas, Nebraska, and southeast
Wyoming. Thirty-eight shorebird species use habitat
in the CP/PLR during migration and 13 of these
species also breed in the region (Fellows et al. 2001).
Of these, 16 species have been identified as species of
primary concern. Based on the Kirwin NWR bird list,
13 of these priority species have been documented on
the refuge, including Snowy Plover, Long-billed
Curlew, Upland Sandpiper, White-rumped Sandpiper,
Baird’s Sandpiper, and Piping Plover (Appendix D).
The national and regional plans should be consulted
for national population objectives, justifications for
species designations, and other pertinent information
(U. S. Shorebird Conservation Plan, URL http://
shorebirdplan.fws.gov/RegionalShorebird/downloads/
CPPLR.doc).
Waterbird Conservation Region
Kirwin NWR is within the Central Prairies Region of
The North American Waterbird Conservation Plan
(NAWCP). In North America, separate initiatives
exist for waterbirds, shorebirds, and waterfowl.
Thus, the NAWCP focuses on seabirds, coastal
waterbirds, wading birds, and marsh birds (Waterbird
Conservation for the Americas, URL http://
www.waterbirdconservation.org/waterbirds/). There
are 23 species listed in the Central Prairies that have
been documented on Kirwin NWR. Of these, the
conservation status of six species are designated as
“not currently at risk”, five are considered of “low
conservation concern”, nine are of “moderate
conservation concern”, and three are of “high
conservation concern” (Kushlan et al. 2002; Appendix
D). The entire plan should be consulted to fully
understand how scores were determined.
Playa Lakes Joint Venture
At a smaller geographic scale, Kirwin NWR is part of
the Playa Lakes Joint Venture (PLJV; URL http://
www.pljv.org/about01.html), which encompasses most
of BCR 18 (Shortgrass Prairie) and BCR 19 (Central
Mixed-Grass Prairie). Joint ventures originally were
conceived by FWS in 1986 to implement the NAWMP.
URL http://northamerican.fws.gov/NAWMP/
nawmphp.htm). However, in addition to waterfowl,
many joint ventures (including the PLJV) are now
incorporating an “all bird” approach. National and
international bird plans provide the foundation for the
PLJV master plan, which sets direction for
conservation activities within the region. Established
in 1989, the mission of the PLJV is to create
sustainable landscapes for the benefit of birds, other
wildlife, and humans. More specifically, the PLJV
directs effort to restore, preserve and protect myriad
habitats, including playas, saline lakes, riparian areas,
and grasslands for resident, wintering, migrating, and
breeding birds. More than 400 species of birds use the
PLJV, including continentally important populations
of waterfowl, shorebirds, other waterbirds, and
grassland birds. The objectives established for the
PLJV in the 1998 update to the NAWMP are to
restore and enhance 4,047 ha (10,000 ac) and 10,117 ha
(25,000 ac) of habitat, respectively, and protect 20,639
ha (51,000 ac) of existing habitat.
collared Longspur) of the Stewardship list species are
known to occur on Kirwin NWR (Appendix D). In
contrast, there are 21 and seven species of continental
importance on the Watch List and Stewardship List in
11
This section has been divided based on general
community designations. This was done to improve
clarity, but it should be recognized that such
distinctions are arbitrary. Communities do not occur
as distinct entities but grade together as evidenced by
the movement of nutrients, energy, and wildlife within
and among communities. Therefore, information for
one community may be relevant for other
communities. Attempts were made to identify these
relationships, but some may have been overlooked.
For each community, a brief history is provided on
historic and current conditions and potential concerns
and opportunities are identified. The inclusion of
historic information is not intended as an effort to
direct refuge management toward restoring
presettlement conditions. Rather, historic
descriptions have been incorporated because they can
provide valuable insight regarding the original
location, extent, and vegetation composition of
communities and changes in abiotic factors (e.g.,
hydrology) that have occurred through time.
Together with information on current conditions,
historic descriptions can be used to (1) identify
important changes in processes that may require
further evaluation and (2) better understand the
potential of refuge lands.
Reservoir (Deepwater)
Historically, there was no deepwater habitat on the
area that now constitutes the refuge. Flows from the
North Fork Solomon River and Bow Creek flowed
unimpeded through refuge lands and occasionally
inundated the floodplain during wet periods.
Construction of Kirwin Reservoir has changed these
conditions. Obviously, damming the flows of the
Solomon River and Bow Creek and impounding water
in the historic floodplain of the rivers created
deepwater habitat. The surface acreage of the
reservoir varies dramatically from about 2,024 ha
(5,000 ac) at conservation pool (527.7 m [1731.25 ft]
elevation) to 356 ha (879 ac) during drought periods
(refuge staff). During the site visit the reservoir
elevation was 522.9 m (1715.6 ft), but water is expected
to drop an additional 3.4 m (11 ft) in the summer of
2003 (refuge staff). These fluctuations likely are due
to a combination of frequent drought periods coupled
with upstream pumping from the aquifer (U.S. Bureau
of Reclamation 2002). Since the mid-1960’s, inflows to
Kirwin Reservoir have declined significantly as
evidenced by a long-term reduction in average annual
inflow of 3,577 ha-m (29,000 ac-ft) between 1920-1964
(6,562 ha-m [53,200 ac-ft]) and 1965-1999 (4,070 ha-m
[33,000 ac-ft]; U.S. Bureau of Reclamation 2002). In
addition, >150 alluvial wells occur above the refuge
(U.S. Bureau of Reclamation 2002). The majority of
these wells are for agricultural uses, but municipal
wells also exist.
There also have been less obvious influences. Prior to
settlement, some amount of sediment was
transported from the uplands to the channel during
storm events. The amount of sediment varied, but
intact upland and floodplain vegetation probably
reduced the amount of sediment that entered the
channel. Following settlement, increased agricultural
activity likely altered the amount and pattern of
sediment transport and deposition in the valley. More
than 50% of the basin is currently cropland (U.S.
Bureau of Reclamation 1984) and cultivation and
intensive grazing in some areas (e.g., areas with large
topographic relief) have likely increased the amount of
erosion, and therefore sediment, entering the
floodplain. Prior to constructing reservoirs in the
Solomon Basin, the distribution of this sediment
varied depending on antecedent conditions and
magnitude of the current event. Following
construction, however, the dams functioned as a
barrier to sediment transport downstream. Thus,
although sediment deposition can occur at various
locations upstream of Kirwin Dam, the dam itself now
represents a terminal location that likely traps the
majority of sediment that enters the reservoir.
The potential impacts of increased sedimentation at
one location are numerous. In terms of quantity,
sediment is the major pollutant of wetlands, lakes,
estuaries, and reservoirs in the United States (Baker
1992). Sediment quality also is an environmental
concern because sediment may act as both a sink and
source for water-quality constituents (U. S. Geological
Survey, URL http://ks.water.usgs.gov/Kansas/
studies/ressed/). Once in the food chain, sediment-derived
constituents may bioaccumulate and pose an
even greater concern to fish, wildlife, and humans. In
addition, sediment loads may never consolidate with
bottom materials. The surface waters in the basin of
the North Fork Solomon River are reported as turbid
with moderate to high concentrations of dissolved
solids (U.S. Bureau of Reclamation 2002). Thus,
increased sedimentation may increase turbidity even
more due to wind and wave action that periodically
suspends sediment throughout the water column.
This could lead to other impacts, including reduced
dissolved oxygen concentrations, altered nutrient
availability, and reduced sunlight penetration. If
sufficient, these changes can eliminate or reduce
growth of submerged aquatic vegetation (SAV) (Robel
1961, Kullberg 1974, Dieter 1990).
The extent that sediment impacts have occurred, or
potentially could occur, in Kirwin Reservoir has
received attention recently. In 1998, the BOR initiated
a sampling program to assess the presence or absence
of organic and inorganic compounds in reservoir
waters. Part of this study involved collecting two
groups of four sediment cores near the dam
(Christensen 1999). Sediment thickness estimated
from these cores ranged from 2.9-3.4 m (9.5-11.3 ft) in
the first group of 4 cores to 2.1-2.3 m (6.9-7.4 ft) in the
second group. Unfortunately, it was not possible to
accurately determine sedimentation rates due to core
shortening (i.e., essentially a partial collapse or
compression of the core that prevented accurate
dating). However, a visual examination of the cores
revealed thick layers of sediment in the deepest
Community Types
12
intervals, which indicates sediment deposition was
greater in the early years of the reservoir. This is
consistent with other reservoir studies (Ritchie et al.
1986; Callendar and Robbins 1993) that have
demonstrated decreased sedimentation rates with
reservoir age. Historical stream flow data indicate
that much of the early sediment deposition in the
reservoir may have been caused by floods during the
1957 and 1960 water years (Christensen 1999).
Another objective of the BOR sampling program was
to determine potential environmental effects due to
elevated levels of total organic carbon (TOC), trace
metals, and major nutrients. The Environmental
Protection Agency has established two threshold
concentrations for many of these elements. The
threshold effect level (TEL) is assumed to represent
the concentration below which toxic effects rarely
occur, whereas the probable effect level (PEL)
indicates the concentration that usually or frequently
results in toxicity. Adverse effects occasionally occur
at concentrations between the TEL and PEL. Both
the TEL and PEL are guidelines used to screen for
possible hazardous chemical levels, but are not
regulatory criteria.
Total organic carbon was measured because various
organic solutes can form complexes that affect metal
solubility (Hem 1992). The median TOC concentration
in the reservoir was 11,600 mg/kg and the trend was
not increasing. There are no published TEL and PEL
limits for TOC; thus, the impact of existing levels is
not readily apparent. However, further investigation
should be conducted to obtain information from other
reservoir studies to ascertain potential impacts of
current TOC levels.
Selenium (Se) is a naturally occurring trace element
common in the marine shales underlying the Solomon
River Basin (see section on Geology). This metal is of
concern because irrigation in other areas underlain by
marine shales has resulted in elevated Se
concentrations that have caused birth defects,
reproductive failure, and death in fish and wildlife (U.S.
Bureau of Reclamation 2002). No TEL or PEL has
been established for Se, but concentrations >4.0 mg/
kg in sediment can result in bioaccumulation in fish
and wildlife (Lemly and Smith 1987). Concentrations
of Se in Kirwin Reservoir bottom-sediment ranged
from <0.3 to 2.2 mg/kg, indicating low potential for
bioaccumulation (Christensen 1999). However, Se did
exhibit a significant increasing trend (P = 0.006) in one
of the two cores, suggesting that concentrations may
be of concern in the future.
Reports by Christensen (1999) and Christensen and
Juracek (2001) also indicate median arsenic (As)
concentrations (range = 4.6-10.0 mg/kg) exceeded the
TEL (7.24 mg/kg) but not the PEL (41.6 mg/kg)
established for this element. However, a significant
increasing As trend was not evident. Arsenic could
originate from many potential sources, including
underlying geologic features (Christensen and Juracek
2001) or pesticides and industrial activities (Pais and
Jones 1997). However, industrial sources are not likely
given the predominance of agriculture in the basin
(Christensen and Juracek 2001). The median
concentration of copper also exceeded the TEL (18.7
mg/kg) as did cadmium in four samples. In contrast,
chromium, lead, nickel, silver, zinc, and mercury
either were not detected or did not exceed TEL limits.
These results clearly indicate that subsequent
monitoring of heavy metals and other water quality
parameters are warranted. Although no significant
effects have been documented, potential for future
issues may arise given evidence of increasing trends
for some metals.
Phosphorous (P) and nitrogen (N) are nutrients
required for plant growth, but excessive amounts can
enter reservoirs from fertilizer runoff or other non-point
pollution sources and create problems. The
median P and N concentration in core samples from
Kirwin was 616 mg/kg and 1,700 mg/kg, respectively.
However, only P exhibited a significant increasing
trend. Although no TEL and PEL limits have been
established for P and N, additional information could
be obtained to better understand potential impacts.
For example, excessive P has been shown to cause
algal blooms that can reduce dissolved oxygen
concentrations and cause fish mortality, or reduce
light penetration to levels that prevent growth of
some aquatic plant species. Information regarding
nutrient levels that result in algal blooms, or cause
other changes in aquatic biota (e.g., plants, animal)
could be used to develop desired thresholds.
Although reservoir water levels are managed by the
BOR, it may be possible for FWS to recommend or
help establish water quality criteria that would
ensure the needs of fish and wildlife are met.
Published information on the type and amount of SAV
in the reservoir was not located during the initial
literature search and the refuge staff was unable to
provide any qualitative observations. This is
unfortunate because plant composition and biomass
occurring in the deepwater community greatly
influences potential wildlife values. Plants capable of
growing in deep water provide substrate for
invertebrates (Krull 1970, Voigts 1976) that, in
combination with plant parts, provide foods for many
different vertebrates (e.g., fish, waterbirds). In
contrast, if SAV is not present, the deepwater
community may only provide roosting and loafing
habitat for birds. To better evaluate this community,
additional searches for information on plant resources
should be pursued, including contact with personnel
from Kansas Department of Wildlife and Parks and
BOR to obtain any reports or documents that may
exist.
Waterfowl counts conducted between 1983 and 2001
document ducks, geese, and swans occurring on the
refuge in varying numbers (Appendix C). On an
annual basis, the primary periods of use occur during
spring and fall migration; however, some species,
primarily Canada Geese and Mallards, remain on the
refuge during some winters (Appendix C, U.S. Bureau
of Reclamation 2002). Both diving ducks and geese use
the deepwater portion of the reservoir. Plant
13
composition and biomass information is lacking; thus,
it is not possible to determine if foraging habitat is
available. Waterfowl surveys only provide weekly
estimates on the entire refuge. Information on
numbers and activities (e.g., foraging, resting) of each
species in individual habitat types (e.g., deepwater
versus shoreline) are lacking. Therefore, this data
cannot be used to speculate on the type and
availability of resources and it is impossible to arrive
at any definitive conclusions. However, at a minimum
it is likely that the deepwater community provides
roosting and loafing habitat for waterfowl (ducks,
geese, swans), as well as sanctuary from shooting
during hunting season (U.S. Bureau of Reclamation
2002). This zone also could provide additional benefits
in the form of foraging habitat if SAV beds or
invertebrates are present. The types of foraging
habitat available would largely depend on the types
and locations of food items. For example, the
presence of pondweed drupelets or invertebrates
within about 46 cm (18 in) of the water surface is
available for dabbling ducks, whereas swans can
access pondweed foliage at greater depths
(Fredrickson and Reid 1986, Fredrickson and Laubhan
1994).
Based on conversations with refuge staff, another
interesting issue that would merit further
investigation is the value of the deepwater zone as
refuge during the hunting season. Currently, this
area is closed to hunting and the staff thinks this
increases the number and duration of time that geese
are in the area. A competing idea is that goose
numbers near the refuge are positively correlated
with the amount of row crops. Sufficient data may be
available to conduct a correlation analysis between the
size and availability of the closed zone, cropland acres,
and goose numbers. Although correlation analysis is
only a “measure of association” and does not prove
cause-and-effect, this analysis may provide some
insight or help identify variables to monitor in the
future.
Management Potential -The ability of FWS to
manage the deepwater habitat is minimal. Reservoir
elevations are determined by other federal entities
that must consider several factors (e.g., irrigation,
flood control) other than wildlife. Hydrology,
including the direction, magnitude, and time of water
level fluctuations, is the primary factor influencing
resource production and availability (Mitsch and
Gosselink 1993, Fredrickson and Laubhan 1994). The
inability of FWS to influence these hydrologic
parameters prevents the ability to reliably stimulate
or maintain desired plant communities and associated
food resources, or influence resource availability (e.g.,
water depth between food resources and water
surface). Even if FWS could establish guidelines
specifically for wildlife, the dramatic fluctuations in
surface area caused by uncontrollable factors (e.g.,
precipitation, upstream groundwater pumping) would
make it difficult to reliably and consistently achieve
desired outcomes.
Although direct management is minimal, the
deepwater community still provides resources that
contribute to the overall value of the refuge.
Therefore, FWS should consider options that can be
used to indirectly influence the values that are
provided as a result of annual reservoir operation.
Potential options to consider include working
cooperatively with BOR to establish water quality
criteria and continuing to maintain existing
agreements that designate a portion of the deepwater
community as a closed area during hunting.
Shoreline
The shoreline and deepwater communities are both
part of the reservoir and, therefore, are functionally
connected both spatially and temporally. They also
share some of the same ecological attributes,
including source and quality of water. However, these
communities have been separated because they are
very different with respect to some hydrologic
parameters (e.g., water depth), plant communities,
and wildlife resources.
Definitions vary, but the shoreline community is
defined in this report as the portion of the reservoir
(excluding the riparian zone) with water depths that
range from saturated soils to <61 cm (24 in). The
general shape of the shoreline is linear, but the width,
and spatial position of this area change both annually
and seasonally depending on reservoir water levels
and bathymetry (i.e., topography of reservoir bottom
sediments). For example, the bathymetry of the
shoreline has been differentially influenced by erosion
following reservoir impoundment. The presence of
deep and shallow cutbacks caused by wave action can
significantly influence habitat suitability for some
species that tolerate a narrow range of water depths
(e.g., shorebirds). The paucity of palustrine wetlands
on the refuge means that the shoreline is the only
community that potentially can provide substantial
foraging habitat for dabbling ducks (unless SAV
occurs in the deepwater community), shorebirds, and
wading birds. However, a sufficient area of suitable
(e.g., proper substrate, water depth) shoreline must
be available if the community is to provide limiting
resources (aquatic invertebrates, seeds, tubers) in
quantities that benefit different waterbird guilds.
Although area estimates of the shoreline community
were not available, the bathymetry and water level
data needed to develop estimates is likely available
from the BOR. The use of this data to develop curves
for estimating shoreline area is highly recommended
because it would likely prove useful in future
discussions regarding management potential and
values of this community. For example, the range of
water depths along the shore at different elevations
could be compared to water depths used by foraging
waterbirds to determine area of suitable habitat
available. In addition, the refuge staff reported that
an agreement exists between certain entities to
maintain conservation pool at 527.7 m (1731.30 ft),
rather than the legal elevation of 527.1 m (1729.25 ft).
The potential impacts (positive or negative) of this
increase on available foraging habitat for various avian
guilds could be estimated using the above mentioned
curves, but would be difficult otherwise.
14
Because area is important, a coarse estimate of 91-271
ha (224-670 ac) for the shoreline community at
conservation pool was derived to provide some
perspective. The accuracy of this estimate should be
viewed with extreme skepticism for several reasons.
First, the estimate uses an assumed average width of
15-46 m (50-150 ft). Exact widths are unknown and
likely vary extensively around the perimeter of the
reservoir. Second, the estimate is based on a shoreline
length of 60 km (37 mi) at conservation pool which
likely includes portions of the shoreline that would be
more appropriately considered the riparian
community. Also, and perhaps most important,
fluctuations in the reservoir surface are known to be
dramatic. Consequently, a single estimate at
conservation pool does not capture the full range of
shoreline area that occurs within and among years.
However, this estimate does suggest that the area of
shoreline is sufficient to warrant further
consideration.
The shoreline potentially can provide unique
resources for a diverse array of avifauna. According
to refuge files, Double-crested Cormorants and Great
Blue Herons have nested on the refuge since 1952 and
1963, respectively. Reproductive effort varies
annually, but between 1960 and 1995 the number of
Great Blue Heron nests has ranged from 1-20 with
production of 2-90 young. During the same period,
Double-crested Cormorant nests and young have
ranged from 3-37 and 40-60, respectively. The current
location of rookeries occurs within, or adjacent to, the
shoreline community near the main reservoir body in
the eastern portion of the refuge. Trees currently
used for nesting appear to be adjacent to stream
channels that were inundated when water was
impounded by the reservoir. Many of these trees were
killed as a result of high water in the 1990’s, but many
remain standing and still provide suitable nesting
habitat.
In addition, Least Terns occasionally nest within the
shoreline community and protection of ground nests is
required. Exposed sandbars constitute the preferred
nesting substrate of Least Terns. However,
substrates similar to sandbars are exposed along the
shoreline when reservoir elevation recedes and some
Least Terns occasionally nest in these areas.
The primary value of the shoreline community, based
on the geographic location of the refuge, likely is
foraging habitat for a variety of waterbirds. This area
constitutes a zone of high biological productivity. The
growth of plants during drawdown results in the
production of food resources (e.g., seeds, tubers) and
the release of nutrients when vegetation decomposes
upon reflooding can be assimilated by small aquatic
organisms (e.g., microinvertebrates) (Fredrickson and
Laubhan 1994). These organisms constitute the
forage base for macroinvertebrates, fish, and
amphibians, which are the primary foods of many
waterbirds. In addition, the hydrologic fluctuations
that occur within this area create numerous
microhabitats that can be used by numerous species.
Herons and other wading birds forage primarily on
aquatic animals, including fish, amphibians, and
macroinvertebrates. Although some species are
capable of capturing prey in water >60 cm (24 in), the
majority of foraging typically occurs within the
shoreline community (e.g., shallow water or along the
water-mud interface) (Fredrickson and Reid 1986).
Except for extreme fluctuations, changes in reservoir
levels likely do not alter production or availability of
fish, the primary food item of these species (but see
Gawlik 2002 for impacts that can occur given the right
circumstances). During drought years, it is
conceivable that fish kills may occur. This may or
may not impact foraging efficiency and nest success of
waders depending on the biomass of foods that remain
during these periods. Although pertinent data was
not located during this initial investigation, Kansas
Department of Wildlife and Parks may have relevant
information.
Ducks (diving and dabbling) and shorebirds also
forage within the shoreline community (Fredrickson
and Reid 1986, Skagen and Knopf 1994). In fact, the
paucity of palustrine wetlands suggests that these
species rely almost exclusively on the shoreline for
foraging when using the refuge. However, refuge
survey data does not provide information to confirm
this assumption. Further, the production and
availability of resources for these species is difficult to
predict because of the dynamic water fluctuations that
occur in this edge community. For example, during
March 2003 vegetation along the northern shoreline
included reed canary grass, saltcedar, and Canada
thistle. There also were extensive areas of bare
ground. Although the production of foods (browse,
seeds, tuber, etc.) for ducks and geese appears
minimal, the growing season had not yet started and
additional plants may germinate. If additional
germination does not occur, the extensive areas of
unvegetated shoreline likely will provide foraging
habitat for spring migrant shorebirds. However,
optimum foraging depths vary among shorebirds
depending on size (i.e., tarsus length); thus, not all
shorebirds would benefit equally. In contrast, a very
different plant community was evident during a field
visit to the refuge in 1999. This visit was conducted
during the growing season and water levels were
much higher. My field notes indicate minimal bare
ground and the presence of smartweed, millet,
bulrushes, cattail, beggarticks, ricecut grass,
spikerush, cocklebur, sedges, and panic grass among
other species. Depending on fall water conditions, the
shoreline would have provided excellent foraging
habitat for dabbling ducks and geese due to the large
biomass of seeds and browse produced. In contrast,
shorebird foraging habitat would likely have been
minimal due to excessive vegetation cover.
The above observations fromt two different years
provide evidence that the seed bank within the
shoreline community is diverse and includes both
desirable (e.g., browse, seed-bearing) and undesirable
(e.g., invasive, exotic) plant species. The species that
germinate from the seed bank, and the ultimate
densities of species that survive, are determined by a
multitude of factors. Most species that germinate in
15
the shoreline area require substrates that are moist
to wet, but not flooded (van der Valk and Davis 1978).
Thus, the most important factor controlling
germination likely is the annual changes in reservoir
water levels, including the magnitude, timing, and
rate of water level fluctuations. These hydrologic
parameters greatly influence recruitment from the
seed bank by affecting time of soil exposure, soil
temperature and oxygen levels, and the rate of soil
moisture loss (Leck 1989, Fredrickson 1991). Water
quality also may be important because constituents
(e.g., salts, iron, copper) in the water are bound by soil
particles at the soil-water interface and can affect
plant germination and growth. This deserves further
investigation because of water quality issues in the
reservoir. However, the diversity of plants that have
already been documented along the shoreline
suggests that water quality currently is not severely
impacting the germination or survival capability of
many species.
Management Potential – Similar to the deepwater
portion of the reservoir, the ability of FWS to manage
the shoreline community is constrained by the lack of
hydrologic control. Consequently, the value of the
shoreline community to waterbirds likely will vary
among species and years. Trees adjacent to the
reservoir and the presence of fish near the shoreline
are probably consistently available. Thus, suitable
habitat for breeding Great Blue Herons and Double-crested
Cormorants, as well as migrating and
wintering Bald Eagles, is usually present on the
refuge in most years. In contrast, foraging habitat for
ducks and shorebirds will be more variable for two
primary reasons. First, it is not possible to
manipulate water levels to match the germination
requirements of plants that produce a large biomass
of foods (e.g., seeds, tubers, browse) and provide
substrate for invertebrates. Second, water levels
cannot be intentionally manipulated to coincide with
duck and shorebird migration periods. Therefore, in
the absence of hydrologic control, some exposed and
vegetated shoreline habitat will be available to
shorebirds and ducks every year, but water level
changes that expose abundant foods during migration
will occur only sporadically. Finally, the availability of
habitat for Least Terns varies, but likely is more
predictable than ducks and shorebirds. This
statement is based on the reported long-term
drought/wet cycle of 30 years with about 23 years of
drought and seven years of wet conditions (refuge
staff). According to the refuge staff, reservoir pool
elevations tend to consistently decrease during the
drought phase. When this occurs, the availability of
substrates suitable for Least Tern nesting tends to
become more reliable, and the probability of nest
destruction due to flooding less likely, during a period
of several years. During the start of the wet period,
water levels in the reservoir start to increase,
available nesting habitat decreases, and, if nesting is
attempted, the likelihood of nests being destroyed by
flooding increases.
Another reality is the potential for an unfavorable
plant community to develop in the shoreline
community. The land-water interface in this zone is a
prime area for the establishment and proliferation of
many invasive species due to the frequent presence of
exposed soil, variable soil moisture, and high nutrient
availability. For example, along the north shoreline
numerous saltcedar seedlings and stems of Canada
thistle and reed canary grass were evident. Although
currently present only in small numbers, the
potential exists for expansion of these invasive species
(or others) along the shoreline, which could result in
the loss of current shoreline values (Sudbrock 1993,
Bailey et al. 2001). Evidence of this potential exists in
the floodplain of the lower riparian zone where reed
canary grass and Canada thistle currently dominate
the herbaceous vegetation (see below).
FWS cannot alter the hydrology of the reservoir to
minimize the potential for invasions of non-natives to
occur. Similarly, FWS cannot intentionally raise pool
elevation to eliminate invasions that do occur.
Nevertheless, the refuge staff is responsible for
addressing invasive species that do occur. Potential
control options (herbicides, fire, mechanical
equipment) exist, but implementation may not be
possible in some years (e.g., too wet). Also, many
techniques often are costly and require repeated
application to be successful. Thus, it is recommended
that decisions be made regarding the ability and/or
desire to conduct such operations under different
conditions. Information available in the literature and
refuge files should be adequate to develop working
hypotheses of potential tradeoffs (e.g., costs, benefits,
probability of success) related to active management
in this community. This information should be
consolidated prior to CCP development.
In summary, the shoreline community has the
potential to provide many values to waterbirds that
other communities on the refuge do not provide.
There also is potential for extensive, rapid colonization
of invasive species. These detrimental impacts are
common on many reservoirs, and approaches to
minimize impacts are often difficult to develop due to
constraints imposed by the reservoir operation plan.
In the case of Kirwin Reservoir, the only
recommendation is to consult with the BOR to
determine if annual operations can be altered slightly
to take advantage of existing conditions that occur in
some years. For example, it is likely that the release
of a relatively small volume of water in spring would
expose a large amount of shoreline habitat around the
reservoir for spring migrant shorebirds. Such
releases would not have to occur annually; rather, an
agreement could be developed that would result in
release only when pool elevations are above a certain
level. In many cases, such alterations may have only
negligible impacts on other reservoir uses but result
in significant wildlife benefits.
Riparian
The riparian community, which includes the floodplain
and channel of the Solomon River and Bow Creek, was
dynamic historically. Although both streams were
considered perennial (Leonard 1952), flows were
highly variable depending on precipitation cycles.
16
Stream hydrology was characterized by flood flows in
the spring and low flows or ponding during the
summer and fall (U.S. Bureau of Reclamation 2002).
These extremes in hydrology influenced the types of
flora that developed and the fauna that inhabited the
riparian system. During major floods the channel was
reworked, vegetation was uprooted, and sediment was
transported downstream and deposited at various
locations in the channel and floodplain. These actions
resulted in the creation of various channel habitats
(e.g., pools, riffles), marsh areas adjacent to the rivers,
and sites for regeneration and growth of various plant
types in the floodplain.
The historic floristic composition of the floodplain
included grasses, forbs, and woody vegetation.
Kuchler (1974) described this community as
“floodplain forest and savanna”, with scattered trees
and shrubs and a dominant ground cover of bluestem
prairie. However, he also states that “the prairie was
suppressed in areas of dense woody growth”,
suggesting that certain areas of the floodplain were
extensively forested. The wooded component
apparently was continuous but narrow based on
accounts of early settlers and one aerial photograph
(Plate 5, page 18 in Leonard 1952) of the Solomon
River near Glade, Kansas. Dominant woody species
included cottonwood, American elm, hackberry, and
peachleaved willow, whereas the dominant herbaceous
vegetation consisted of big bluestem, little bluestem,
switchgrass, and Indian grass. In contrast, marshes
were dominated by prairie cordgrass and lesser
numbers of myriad species, including bulrushes,
cattail, and rice cutgrass (Kuchler 1974).
The historic wildlife community inhabiting the
riparian community was diverse and unique. Forests
were rare in the Great Plains and the woody
vegetation provided cover, forage, and nesting
substrates for neotropical migrants that were not
available in other communities. The tall grasses
provided important resources for both migratory and
resident wildlife, and marshes provided resources for
a host of waterfowl. The stream fishery was not rich
and included only species (e.g., plains killifish, red
shiner, creek chub) that could tolerate extremes in
hydroperiod, temperature, current velocity, and
dissolved oxygen concentrations (U.S. Bureau of
Reclamation 2002).
However, as with other communities on the refuge,
human settlement and the accompanying changes
have greatly altered processes and influenced
vegetation in the riparian community. Among the
most important changes include reservoir
construction, increased groundwater pumping,
diversion dam construction, and irrigation canal
development (Christensen and Juracek 2001). The
potential range of impacts caused by these changes
varies from subtle to obvious depending on the year
and antecedent environmental conditions. The upper
portion of the riparian community differs greatly from
the lower portion due to the impacts of the above-mentioned
changes.
woody riparian vegetation on the Solomon River (3,112
ha [7,689 ac]) ranked second only to the Lower
Arkansas (5,083 ha [12,560 ac]) (Eddy 1994). The
composition of trees in the mid-1990’s was dominated
by eastern cottonwood (58%) and willow (25%) with
lesser amounts of American elm (4%) and green ash
(3%), hackberry, boxelder, and mulberry (Sevigny
1998, Eddy 1994). The shrub and vine component (5%)
also was evident, but some non-native trees have
invaded the system, including saltcedar (Eddy 1994),
Siberian elm, and honey locust (Sevigny 1998, refuge
staff). Perhaps the greatest change from historic
structure and composition has occurred in the ground
vegetation. The once dominant tall, warm season
grasses described by Kuchler (1974) have been
replaced by shorter cool season grasses (e.g., smooth
brome), which has altered structural and floristic
diversity (refuge staff, personal observation).
The avian community also remains diverse, which is
not surprising. The ability of riparian systems to
support a diverse assemblage of vertebrates is well
documented (Pashley et al. 2000). However, the
composition and relative abundance of species have
likely changed due to landscape level changes in land
use (e.g., agriculture). In 1997, a study of the riparian
bird community on the refuge during spring migration
resulted in the identification 87 species from 19
families (Sevigny 1998). A detailed inspection of this
list identified some intriguing (although not
substantiated) aspects that may be related to changes
in ground flora. The nine most abundant species
(>100 recorded) were the House Wren, Blue Jay,
Black-capped Chickadee, Mourning Dove, Northern
Cardinal, Common Yellowthroat, Red-winged
Blackbird, and Brown-headed Cowbird. Based on
Breeding Bird Survey (BBS) data for Region 6 of
FWS, the Black-capped Chickadee (n = 257 routes,
trend = 0.9, P = 0.19, 95% confidence interval [CI] = -
0.4 – 2.1), Mourning Dove (n = 568 routes, trend = 0.0,
P = 0.82, 95% CI = -0.4 – 0.5), Northern Cardinal (n =
73 routes, trend = 1.1, P = 0.06, 95% CI = 0.0 – 2.2),
Common Yellowthroat (n = 322 routes, trend = 0.1, P
= 0.89, 95% CI = -0.8 – 0.9), Red-winged Blackbird (n
= 525 routes, trend = 0.1, P = 0.84, 95% CI = -0.5 –
0.6), and Brown-headed Cowbird (n = 533 routes,
trend = 0.1, P = 0.71, 95% CI = -0.4 – 0.6) exhibited
stable populations trends, whereas the House Wren (n
= 410 routes, trend = 2.4, P = 0.00, 95% CI = 1.8 –
3.1) and Blue Jay (n = 179 routes, trend = 0.8, P =
0.02, 95% CI = 0.1 – 1.6), exhibited increasing
population trends between 1966 and 2003 (Sauer et al.
2004, URL http://www.mbr-pwrc.usgs.gov/bbs/
bbs.html). Further, most of these species are capable
of adapting to changes occurring in the riparian
communities throughout the western United States
(Saab 1999). In contrast, however, the list also
included 19 species whose status is of some concern
according to current regional and national plans
(Appendix D). The presence of these species in low
In the mid-1990’s, the floodplains of both streams
supported trees on the refuge, but the width varied
from a few scattered trees to areas as wide as 180 m
(590 ft) (Sevigny 1998). Of the nine river systems in
the western two-thirds of Kansas, the amount of
17
abundance suggests the riparian plant community has
not been completely altered, but subtle, significant
changes have occurred that has reduced habitat
suitability for some species. Additional investigation
to identify these changes and their causes would be
valuable for determining appropriate future
management actions. However, given the impacts of
high water during the mid-1990’s (see below) the
preceding statement only applies to the upper portion
of the riparian community.
Comparing shifts in avian communities between
historic and current periods often is used as a
technique to describe community changes. This
approach has much value, but it also has several
weaknesses. First, this technique cannot identify all
changes that potentially have occurred. Second,
changes in processes often can only be detected by
certain avian parameters (e.g., abundance, nest
density); thus, multiple parameters often must be
collected and this data is rarely available in historic
accounts. Finally, these comparisons only illustrate
past trends and do not identify cause-effect
relationships. Consequently, they provide little
information on future expectations, particularly in
environments that are subject to rapid and extreme
changes due to human events (see below).
To remedy this shortcoming, information regarding
change in processes that influence community
structure and function also must be developed.
Traditionally, ecologists assumed that the most
important processes affecting populations operated at
local spatial scales (Carothers et al. 1974, Urban and
Smith 1989). Recent research, however, has indicated
that larger scale assessment also should be
considered (Wiens 1989, Forman 1995). These large
scale assessments can help (1) identify changes that
are preventing desired conditions from being obtained,
(2) identify future management actions that are likely
to be most effective, and (3) determine if management
is feasible or warranted. Often, as is the case with the
riparian community, the evaluation largely is
subjective because all the required information is not
available. However, a combination of available
information integrated with logic and general
principles of how processes affect community
structure and function can still provide valuable
insight for making management decisions. The
following information has been developed based on this
perspective.
Increased groundwater pumping, canals, diversion
dams, and reservoir construction have all contributed
to altered stream flow in both streams (Christensen
and Juracek 2001). However, the impacts to the
riparian community caused by pumping, diversion
dams and canals differ in some ways from those
caused by the reservoir and will be discussed
separately. The first three activities occur above the
refuge, are associated largely with agriculture, and
have changed the annual hydrograph by reducing the
volume of water in the channel and changing the
timing of peak and low periods (Wis. Bureau of
Reclamation 2002).
Exact shifts should be determined by analyzing long-term
hydrographs (if available). However, compared
to historic conditions, the general effect is that larger
storm events or longer wet periods are required to
cause the same amount of overbank flooding and
channel scouring. The periodic occurrence of these
actions is critical to maintaining channel diversity
(e.g., pools, riffles) and creating conditions suitable for
germination of new woody and herbaceous vegetation.
In addition, the long-term average depth to the water
table underlying the floodplain has likely increased.
This change has occurred because the groundwater in
the floodplain is in direct connection with water in the
channel (see sections on Geology and Groundwater).
In general, these two entities are in dynamic
quilibrium. Due to upstream influences, the volume,
and therefore depth, of water in the channel has
decreased during non-flood periods. As water depth
has decreased, free water (i.e., not bound by soil
particles) in the ground has likely seeped into the
channel until equilibrium is reached or no more
groundwater is available. The greater the drop in
channel water depth (e.g., during extreme drought),
the more likely groundwater will seep into the
channel. Ultimately, these changes can result in
decreased soil moisture in the rooting zone of the
floodplain. This can impact plant community
composition and structure because altered soil
moisture can influence germination potential of seeds
and affect the growth of existing plants. Site-specific
information necessary to confirm these changes and
determine if the magnitude of change has been
sufficient to alter plant composition is not available,
but it is recommended that data be collected. This
can be accomplished by refuge staff using relatively
inexpensive methods and would be valuable in
determining future management actions.
Construction of the reservoir occurred immediately
downstream of the riparian community managed by
the refuge. Similar to upstream hydrologic
alterations, the dam has reduced flow velocity in the
stream because water no longer can be transported
downstream unobstructed. Historically, these events
were important because floodplain vegetation was
disturbed and areas suitable for new germination were
created. The reduced frequency or absence of these
events likely lowers the potential of bare, moist
substrate necessary for regeneration of species such
as cottonwood and willow (Scott et al. 1993). In
addition, the reservoir functions to store water during
wet years. During prolonged wet periods, or during
extreme precipitation events, the impoundment of
floodwaters can result in inundation of the floodplain
to deeper depths and for longer periods than
historically occurred. If inundation lasts a sufficient
time it can lead to the mortality of vegetation (Teskey
and Hinckley 1977). Also, the release of water from
the reservoir is timed to coincide with irrigation needs,
usually summer and early fall (U.S. Bureau of
Reclamation 2002). This, in combination with
upstream activities, has changed the period of
maximum stream flow from spring to summer. This
shift has several impacts, but one of the most
important is the potential effect on germination of
18
riparian vegetation. Seeds of many species, including
cottonwood and willow, are dispersed in spring, are
short-lived, and require bare, moist substrate for
germination. Thus, the shift from spring to summer
flows can negatively impact germination of these
species.
During certain years, or combinations of years, the
effect of these impacts can result in severe and long-lasting
effects on riparian vegetation. This is obvious
based on the damage to riparian vegetation caused by
the most recent wet period (1993-2000). This damage
was still evident in March 2003 and illustrates
potential management issues that should be
addressed during CCP development. A general
chronological description of events follows:
1. A period of high water starts in 1993 with a 140 cm
(55 in) rain event (U.S. Bureau of Reclamation 2002,
refuge staff). The riparian study (Sevigny 1998) was
being conducted at about this time.
2. Water levels in the reservoir increase enough to
back water into the lower portion of the riparian zone
immediately upstream of the reservoir.
3. The water remains at depths long enough in the
lower portion to kill all but 142 ha (350 ac) of riparian
vegetation (U. S. Fish and Wildlife Service 1996).
Although mortality was not as evident in the upper
riparian zone, it is likely that this area was also
impacted to some extent. For example, water in the
upper channel could not be evacuated downstream
until water was released from the reservoir. Thus,
some of the same plant species (e.g., reed canary
grass, Canada thistle) that became established in the
lower riparian zone also became established in low
elevation portions of the upper zone.
4. The wet period ends in 2000 and water recedes
between 2001 and 2003. To facilitate crop irrigation
downstream, releases occur primarily during summer
months (U.S. Bureau of Reclamation 2002).
5. The release of water is slow and scouring does not
occur in either the channel or floodplain.
6. Germination of woody vegetation is minimal
because bare, moist substrate is not available during
spring when seeds of cottonwood and willow disperse
from surviving parent trees.
7. Germination of herbaceous plants occurs, but
species composition is dominated by reed canary
grass and Canada thistle. This is expected since
seeds and rhizomes of these species are adapted to
growth in moist, warm soils that frequently occur
with summer removal of water.
8. In the spring of 2003, the floodplain consists of
standing, dead timber with an understory of Canada
thistle and reed canary grass.
This scenario likely occurs infrequently based on the
fact that it has occurred only once since reservoir
construction in 1952. This is not surprising based on
information provided by the refuge staff that the long-term
drought/wet cycle spans a 30-year period with
about 23 years of drought and seven years of wet
conditions. Because the most recent wet period (1993-
2000) ended three years ago, reservoir water levels
should continue to decline over the next 20 years.
However, even if these long-term predictions are
correct, the impacts of recent high water have been
severe. Tree mortality has been significant,
regeneration of the woody component is sparse, and
non-native vegetation has replaced natives in the
understory. Undoubtedly, such changes have also
altered the avian community from what was reported
in the mid-1990’s. Perhaps more important,
restoration will be costly in terms of both money and
labor. Some of the dead timber may have to be
removed, the invasive species controlled, and suitable
conditions for regeneration of desirable trees and
grasses created. Therefore, it is recommended that
more information be obtained regarding the
relationship between reservoir pool elevations and the
duration and depth of floodplain inundation for
different reaches of the riparian community. This
would help in determining the potential costs,
benefits, and reliability of managing different portions
of the riparian community. Several techniques could
be used to develop information on flooding depth in the
floodplain. The most comprehensive (e.g., full range
of estimates) and accurate technique would involve the
use of bathymetry or topographic data that
encompasses both the reservoir and tributary
streams. Alternatively, current aerial photographs of
the reservoir at different pool elevations could be used
to estimate relationships. Data on flood frequency
and duration can be developed based on the number of
times and duration the reservoir pool exceeded certain
elevations, respectively.
Management Potential – Streams, and their
associated floodplains, are complex ecological systems
that provide many benefits to society. Throughout the
western United States, these areas are valued as a
source of water, recreational activities, and the unique
plant and wildlife resources they support. Due to
these myriad values, they also are among the most
highly modified systems. Usually a single stream is
owned and managed by multiple entities for purposes
that often conflict to some extent. Thus, the ability to
successfully manage a reach for a specific outcome is
often influenced by uses both upstream and
downstream of the site.
Although the above description is generic and applies
to many streams, it aptly describes the portions of the
North Fork Solomon River and Bow Creek managed
by FWS. The values of this community are still
apparent based on available data. However, past
alterations both upstream and downstream of the
refuge have caused significant changes that affect the
ability of FWS to maintain the functions and processes
that supported the historic riparian community. Of
primary concern are the hydrologic alterations that
result in extreme water level fluctuations in the
floodplain. High water similar to that experienced in
the mid-1990’s may occur infrequently, but the cost of
restoring the native community following such events
19
likely will be time-consuming and costly. Further, this
effort may be required every 20-30 years based on
long-term predictions. Potential solutions that
address the entire riparian community are not readily
apparent because release of water from the reservoir
during high flow periods would be required. This is
not likely since a primary reason for reservoir
construction was to store this water for irrigation
below Kirwin. If a viable solution is not found, it is
recommended that the benefits and costs associated
with managing different portions of the riparian
community be evaluated. This may result in the
identification of portions that are relatively free of
reservoir impacts. Part of this analysis would require
determining the likelihood that certain reservoir
elevations will occur during a given time period and
estimating the riparian area impacted at these
elevations. For example, a reservoir elevation of 528.8
m (1735.0 ft) would likely occur 2 times every 20 years.
At this elevation, 20% of the riparian community
would be flooded to depths that cause significant
damage. Based on these probabilities, the riparian
community could be divided into areas that are
frequently and infrequently prone to reservoir
impacts. Each of these areas could be addressed
differently. For example, the area not prone to
reservoir impacts could be managed to provide the full
range of floristic composition and structure desired
with a high level of probability that progress would
not be impacted by the reservoir. In contrast,
management effort in the area frequently
experiencing reservoir impacts would differ because
the benefits would be short-term and the cost
excessive. This does not mean that this portion of the
riparian community would be abandoned; rather a
different set of management goals would be developed
that take into account uncontrollable factors.
Upland
Kirwin NWR is within the central dissected, or mixed-grass,
prairie region that historically was dominated
by the bluestem-grama association (Launchbaugh and
Owensby 1978). This association was prevalent on
uplands in west-central Kansas, but also extended
west on breaks into the dissected parts of the High
Plains where the grama-buffalo grass prairie
dominated the landscape. According to Kuchler
(1974), the bluestem-grama association is
characterized by dense communities of grasses and
forbs that often are in two distinct layers: one of low-growing
grasses and one of medium tall grasses and
forbs that is usually more open. Dominant species are
big and little bluestem, sideoats grama, and blue
grama. Other characteristic species include western
wheatgrass, western ragweed, leadplant, purple
threeawn, hairy grama, buffalo grass, Freemont’s
clematis, purple coneflower, and Canada wildrye
among others.
Factors historically controlling the distribution and
physiognomy of the mixed-grass prairie included
precipitation, fire, and herbivory. The plant species
composing this prairie are sensitive to major
precipitation fluctuations; thus, their distribution
tends to move east and west in response to alternating
periods of intense drought or wetness (Kuchler 1967,
1972). Summer fires (Sauer 1950) and herbivory
(Dyksterhuis 1958) also helped maintain the prairie by
suppressing woody vegetation. However, certain
woody plants were always present as natural
components in some areas (Kuchler 1974).
Herbivores, including bison and smaller vertebrates
such as prairie dogs, altered soil characteristics and
other factors that influenced plant establishment and
growth (Kuchler 1974).
Following the onset of human settlement, however,
processes were modified that profoundly affected the
prairie (Knopf and Samson 1997). Fire suppression,
development and expansion of agricultural crops,
changes in herbivores and herbivory, and planting of
trees have significantly altered the prairie landscape.
In addition, technological advances brought about
other less obvious but equally important changes,
including the development and introduction of new
grasses and crops, groundwater pumping, herbicides,
and fertilization. These and other actions have
resulted in significant loss and fragmentation of the
prairie community. For example, currently about 60%
of Kansas lands are used for agriculture. Of this 60%,
about 48% is cropland and the other 12% is non-native
grasses (e.g., brome) or CRP (seeded natives).
The condition on Kirwin NWR is representative of the
conditions for Kansas as a whole. The refuge
encompasses about 2,833 ha (7,000 ac) of uplands at
conservation pool and 2,712 ha (6,700 ac) at a pool
elevation of 527.7 m (1,731.3 ft). Grasslands dominate
this acreage, but the refuge staff reports that only
about 81 ha (200 ac) of native grass occur on the
refuge. The remainder is either pasture or reseeded
grass. Further, much of the native grass is isolated
(i.e., fragmented) and occurs in small blocks. Other
habitats occurring in the uplands include shelterbelts,
croplands, chalk bluffs, and a few temporary
wetlands. Although the exact area of shelterbelts is
not known, many appear to be 15-31 m (50-100 ft) wide
and extend for various distances along roads and fence
lines. The tree composition includes a mix of both
hardwood and evergreen species. Wheat, sorghum,
corn, and alfalfa are the dominant crops on the refuge
and approximately 486 ha (1,200 ac) are planted
annually when the reservoir is at an elevation of 527.1
m (1729.25 ft). The cropping program is designed to
prepare agricultural land for conversion to grass and
provide foods for migratory birds and resident
wildlife. Farming is accomplished using cooperative
farmers and arrangements vary depending on crop
(refuge staff). For example, the refuge share of row
crops is 25%, whereas stubble constitutes the refuge
share of wheat.
Chalk outcroppings occur at higher elevations in the
uplands, whereas only a few palustrine wetlands occur
in depressional areas. Both of these communities
exist as small, disjunct areas that compose only a
small percentage of refuge lands. Although not
covered in this report due to lack of information, both
support some distinctive plant species and constitute
unique habitats on the refuge. Thus, additional
information should be obtained regarding their
locations, sizes, and unique resources.
20
Most of the remaining discussion uses the grassland
component of the uplands as the baseline condition.
This approach was used because comparing and
contrasting the values and management options of
multiple plant communities without a standard for
comparison is confusing. Grassland was selected as
the standard because it represents the historic plant
community and presently dominates the uplands.
Also, the values and methods of managing other
habitats (e.g., corn, shelterbelts) in the uplands are
largely known and require little discussion.
Although much of the historic prairie on the refuge
was converted or degraded prior to establishment,
this community (excluding areas adjacent to the
reservoir) appears to be the least effected by the
reservoir. Consequently, FWS has more direct
control and can likely influence future conditions
more reliably. In general, the current condition of
refuge grasslands varies greatly. There are small
areas, many on the south side of the reservoir, that
contain a high proportion of native grass and forb
species. In contrast, other areas are primarily
composed of non-native, cool season grasses. The
dominant non-native species is smooth brome, but
small areas of Kentucky bluegrass also are present
(refuge staff). Finally, areas in various stages of
restoration also occur on the refuge. Species
composition of these stands is mixed, with the
presence of both warm season natives and cool season
non-natives. Unfortunately, more detailed information
on the current condition of the grasslands is lacking.
Maps depicting the locations and sizes of different
grassland types (native, reseeded, tame) are not
available, and both qualitative and quantitative
information regarding the floristic composition
(species of grasses, forbs) and structure of each type
are unknown. Although all information is rarely
available, the lack of at least some of the above
information renders any comments incomplete and
speculative. Therefore, the following information is
provided as a recommendation regarding the types of
information that should be developed prior to CCP
development. In addition, examples are provided
regarding potential uses of this information for
developing future management direction.
First, the locations and floristic composition of the
different grassland types should be determined. The
most proficient method would be to develop a digital
vegetation map based on floristics rather than generic
terms such as pasture, reseeded grass, or native
grass. The latter terms can be misleading if labels
are not applied based on floristic attributes and often
do not convey sufficient information to determine
current value or management options. For example,
the designation of native grass on the refuge appears
to be based on the premise that the ground has never
been plowed (e.g., unbroken sod is another frequently
used term). Such a designation may be correct and
provide some information, but definitions based solely
on past management actions (or lack thereof) do not
guarantee that floristic composition and/or structure
are representative of the historic native community.
For example, invasive grasses (e.g., smooth brome)
can invade areas never plowed and alter plant and bird
community composition and structure (Wilson and
Belcher 1989). Therefore, there is also no guarantee
that the plant community will provide suitable habitat
for vertebrates (e.g., birds) and invertebrates (e.g.,
butterflies) that are an important part of the
grassland community.
Second, the current value of the different grassland
communities identified during vegetation mapping
must be determined. Many vertebrates and
invertebrates exhibit plasticity and can tolerate
certain changes in plant composition and/or structure.
Thus, certain non-native communities, or mixed
native/non-native communities, may provide sufficient
value to warrant maintaining on the refuge. For
example, row crops and wheat provide foods for select
species of waterfowl, shelterbelts provide suitable
habitat for certain songbirds, and CRP plantings that
often include some non-native species provide benefits
to some grassland birds. The benefits provided by
these habitats must be compared to the potential
benefits that would result from converting portions of
these areas to other types. For example, shelterbelts
provide habitat for some songbirds, but represent
“hostile environments” that can hinder breeding by
some grassland bird species. Thus, removing
shelterbelts to increase the contiguous area of
grasslands above a threshold size may benefit
grassland birds but negatively impact songbird
numbers. Such tradeoffs should be documented prior
to making management decisions. Part of this
analysis should also involve evaluating the spatial
attributes (e.g., size, location) of each community.
Appropriate floristic composition and structure is
important, but many species also require areas of
certain size, or multiple communities in close
juxtaposition, to adequately meet life history
requisites (Herkert 1994, Helzer and Jelinski 1999,
Walk and Warner 1999). For example, some species of
grassland birds known to occur on the refuge exhibit
minimum area requirements for nesting. Therefore,
the grassland areas that have been developed for
public use may not constitute suitable habitat because
the extensive road network may have fragmented
these areas sufficiently, regardless of human activities
associated with these areas.
Although a large amount of information exists on
species-habitat relationships, attempts often are made
to assess values based on opinions and past
experiences. This often results in confusion and
conflict. Therefore, it is recommended that objective
information be developed prior to discussing the
relative merits of each community. This may seem
daunting, but much of the information on bird-habitat
relationships has already been compiled for many
species known to occur on the refuge, and additional
research could be conducted. The digital vegetation
map also would prove invaluable because it could be
used to assess size of each community or distances
between communities.
Third, the benefits and detriments of altering the
type, size, or spatial location of various communities
should be evaluated. For example, the removal of
shelterbelts and/or cropland in certain areas may not
21
result in the creation of contiguous grassland that
exceeds a threshold required to meet the needs of
certain avian species. In such cases, the costs of
conversion would not be warranted because it would
not result in expected benefits. Similarly, the public
use facilities may fragment grasslands in the eastern
portion of the refuge sufficiently to preclude nesting
by some wildlife. If this were true, the benefits of
managing these areas to provide specific structural
conditions may not be worth the cost. If a digital
vegetation map were available, various scenarios could
be portrayed graphically to determine the best
configuration and size of different community types.
Finally, information should be developed to evaluate
the potential of accomplishing different activities. For
example, statements made by the refuge staff suggest
that the current conditions of most existing
grasslands are not desirable. If an evaluation
confirms this statement, then decisions must be made
regarding the potential for different grassland areas.
An initial step could involve classifying each grassland
tract as being in need of either restoration or
maintenance. This is an important distinction because
maintenance implies that the existing floristic
composition is acceptable and management is directed
toward altering structural components (e.g., litter
depth, height, density). Although not everything is
known, the use of tools (fire, herbivory, mowing) to
maintain grasslands has received considerable
attention by the scientific community and general
concepts exist regarding appropriate techniques. In
contrast, true “prairie” restoration is much more
difficult. A review of the literature suggests some
techniques have reliably proven successful in
establishing some components of prairie (e.g., warm
season grass), but much remains to be learned
regarding restoration of all components (e.g., forbs,
native cool season grasses). This is particularly true
of mixed-grass prairie. Little definitive information
exists that provides guidance in determining
appropriate site preparation, seed mixtures, or time
and rate of seeding for different components relative
to specific site conditions (e.g., soil type, groundwater
table).
The lack of information for the existing grassland
communities, in combination with the lack of proven
restoration techniques for mixed-grass prairie,
suggests that attempts to convert existing upland
communities to native prairie will be difficult.
However, this does not mean that an attempt should
not be made. Rather, it indicates that success will
require much work over numerous years (Kindscher
and Tieszen 1998, Fuhlendorf et al. 2002), development
of appropriate monitoring techniques, and frequent
experimentation. An extensive search of the
literature and consultations with local experts likely
will provide initial guidance useful for identifying
potential attributes that may influence restoration
potential. This information could then be used to
refine additional searches for refuge-specific
information on these attributes. For example, if
depths to groundwater or certain soil characteristics
are deemed important, this information could be
obtained from various sources and evaluated to
determine the most likely locations to attempt
restoration.
Management Potential – In many respects, FWS can
exert the greatest influence on the upland community
compared to other community types. However,
constraints still exist that will influence future
conditions. Uplands adjacent to the reservoir are
wetter during high water years and extensive
groundwater pumping upstream of the refuge likely
has altered the subsurface hydrology of some upland
habitats. The effects of these alterations are
unknown, but research indicates change in the water
table can effectively alter environmental conditions
and, therefore, plant species occurrence (Currier
1988). Thus, literature reviews should be conducted
to determine potential changes in abiotic conditions
that would preclude certain management options. For
example, restoration of native grasses and forbs
adjacent to the reservoir may not be feasible due to
changes in soil characteristics. If this is the case,
another grassland type or habitat should be
considered. In addition, invasive species have altered
floristic and structural attributes of many grassland
tracts. Although techniques have been developed for
controlling many of these species, desirable
vegetation must be established following control or
there are no long-term biological benefits. The ability
to accomplish this task largely will depend on what is
considered a desirable community. Depending on the
types of natural resource benefits the core team
decides the refuge should provide, grasslands ranging
from native mixed-grass prairie to CRP or tame
grasses may be appropriate. Some of these types can
be developed with a high degree of certainty, whereas
others are very difficult to establish and maintain.
Finally, some plant communities (e.g., shelterbelts,
croplands) and the public use facilities were not
present historically. Although such features may be
considered obstructions from the perspective of
historic conditions, they provide values that cannot,
and should not, be ignored. Therefore, decisions must
be made regarding the appropriate mix of historic and
current conditions. These decisions will likely
influence the types and configuration of the different
communities composing the uplands.
22
Public Use
In addition to wildlife benefits, the refuge provides
various forms of public recreation that should be
mentioned. At conservation pool there are 1,402 ha
(3,465 ac) of surface water (68.4% of reservoir) open to
activities such as boat fishing, water skiing and jet
skiing. In addition, about 41 ha (100 ac) of grassland
adjacent to the main body of the reservoir are
developed for public use, including shore fishing,
camping, and picnicking (U. S. Bureau of Reclamation,
URL http://www.usbr.gov/gp). There is also an
extensive road network, including a tour loop around
the perimeter of the refuge. Finally, hunting (deer
and waterfowl primarily) is allowed in both the
riparian and upland communities. Given the number
and types of recreational visits to the refuge (U.S.
Bureau of Reclamation 2002), it is possible that human
activities could represent a disturbance that impacts
some species that use the refuge. Peak waterfowl and
shorebird migration periods do not appear to coincide
with peak recreational periods (refuge staff).
However, ground nesting ducks (e.g., Gadwall,
Mallard), Least Terns, grassland birds, and species
that nest in trees adjacent to deepwater habitat (e.g.,
Double-crested Cormorants, Great Blue Herons, and
Bald Eagles) are present during the summer
recreational period. Various regional and national
plans consider populations of some of these species to
be of concern (Appendix D) and information is
available that indicates human activities can interfere
with the successful rearing of young of these species.
Despite these observations, which only allude to
possibilities, there is not sufficient evidence to either
confirm or discount conflicts. However, the fact that
human-wildlife conflicts may occur identifies the need
to develop specific information regarding potential
detrimental impacts to wildlife. Scientific information
addressing the effects of disturbance is available, but
conditions on Kirwin NWR may differ from those
reported elsewhere. Thus, definitive resolution of this
concern may require conducting an appropriately
designed monitoring program or research study on
the refuge. Regardless of the source, this information
could be used to develop solutions that eliminate or
minimize impacts without negatively impacting public
use opportunities.
Finally, the refuge staff has responsibility for
enforcing regulations and maintaining facilities
associated with recreational activities. Currently, the
staff estimate that possibly 50 to 60% of their time is
annually devoted to tasks associated with the public
use program (refuge staff). This amount of effort,
although often warranted, should be evaluated relative
to the time required to achieve the biological goals
established in the CCP. FWS should use this
evaluation to determine an appropriate balance
between natural resource and public use
management, and adjust budgetary and time
requirements to meet these needs.
23
Literature Cited
Albertson, F. W. 1937. Ecology of mixed prairie in west central Kansas. Ecological Monographs 7:481-547.
American Ornithologists’ Union. 1998. Check-list of North American Birds. 7th edition. American
Ornithologists’ Union, Washington, D.C.
American Ornithologists’ Union. 2000. Forty-second supplement to the American Ornithologists’ Union Check-list
of North American Birds. Auk 117:847-858.
American Ornithologists’ Union. 2002. Forty-third supplement to the American Ornithologists’ Union Check-list
of North American Birds. Auk 119:897-906.
American Ornithologists’ Union. 2003. Forty-fourth supplement to the American Ornithologists’ Union Check-list
of North American Birds. Auk 120:923-931.
Bailey, J. K., J. A. Schweitzer, and T. G. Whitman. 2001. Saltcedar negatively affects biodiversity of aquatic
macroinvertebrates. Wetlands 21:442-447.
Baker, L. A. 1992. Introduction to nonpoint source pollution in the United States and prospects for wetland use.
Ecological Engineering 1:1-26.
Callender, E., and J. A. Robbins. 1993. Transport and accumulation of radionuclides in stable elements in a
Missouri River system. Water Resources Research 29:1787-1804.
Carothers, S. W., R. R. Johnson, and S. W Aitchison. 1974. Population structure and social organization of
southwestern riparian birds. American Zoologist 14:97-108.
Christensen, V. G. 1999. Deposition of selenium and other constituents in reservoir bottom sediment of the
Solomon River Basin, north-central Kansas. U.S. Geological Survey, Water Resources Investigations Report 99-
4230.
Christensen, V. G., and K. E. Juracek. 2001. Variability of metals in reservoir sediment from two adjacent basins
in the central Great Plains. Environmental Geology 40:470-481.
Currier, P. J. 1988. Plant species composition and groundwater levels in a Platte River wet meadow. Pages 19-24
in T. B. Bragg and J. Stubbendieck, editors. Proceedings of the 11th North American Prairie Conference.
University of Nebraska, Lin

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A Preliminary Biological
Assessment of Kirwin
National Wildlife Refuge
Biological Technical Publication
BTP-R6004-2004
U.S. Fish & Wildlife Service
A Preliminary Biological Assestment of Kirwin
National Wildlife Refuge
Biological Technical Publication
BTP-R6004-2004
Murray K. Laubhan
U.S. Geological Survey, Northern Prairie Wildlife Research Center
8711 37th Street SE, Jamestown, North Dakota, USA 58401
U.S. Fish & Wildlife Service
Author Contact information:
Murray K. Laubhan, U.S. Geological Survey,
Northern Prairie Wildlife Research Center, 8711 37th
St. SE, Jamestown, ND 58401.
Phone: 701/ 253 5534,
Fax: 701/ 253 5553
Email: murray_laubhan@usgs.gov.
For additional copies or information, contact:
Wayne J. King, USFWS Region 6, Regional Refuge
Biologist. P.O. Box 25486 Denver Federal Center
Denver, Colorado 80225-0486
Phone: 303/236 8102
Fax: 303/236 4792
Email: wayne_j_king@fws.gov
Recommended citation:
Laubhan, M. K. 2004. A preliminary biological
assessment of Kirwin National Wildlife Refuge,
Phillipsburg, Kansas. U.S. Department of Interior,
Fish and Wildlife Service, Biological Technical
Publication, BTP-R6004-2004, Washington, D.C.
Series Senior Technical Editor:
Stephanie L. Jones, USFWS, Region 6 , Nongame
Migratory Bird Coordinator, P.O. Box 25486 Denver
Federal Center Denver, Colorado 80225-0486
Associate Editor:
Wayne J. King, Regional Refuge Biologist USFWS,
Region 6, P.O. Box 25486, Denver Federal Center,
Denver, Colorado 80225-0486
Table of Contents
Summary .......................................................................................................................................................... 1
Acknowledgments ........................................................................................................................................... 2
Introduction ..................................................................................................................................................... 3
Description ....................................................................................................................................................... 4
Refuge Establishment and Authorities .......................................................................................... 4
Location and Topography ................................................................................................................. 4
Climate .............................................................................................................................................. 5
Geology .............................................................................................................................................. 5
Groundwater ..................................................................................................................................... 6
Soils ................................................................................................................................................... 6
Vegetation ......................................................................................................................................... 6
Wildlife Conservation ...................................................................................................................................... 8
Kirwin National Wildlife Refuge ...................................................................................................... 8
State of Kansas ................................................................................................................................. 8
Bird Conservation Region ................................................................................................................. 9
Birds of Conservation Concern ........................................................................................................ 9
North American Waterfowl Management Plan ............................................................................. 9
Partner’s In Flight North American Landbird Conservation Plan............................................10
Shorebird Conservation Region ......................................................................................................10
Waterbird Conservation Region .....................................................................................................10
Playa Lakes Joint Venture ..............................................................................................................10
Community Types ..........................................................................................................................................11
Reservoir (Deepwater) ....................................................................................................................11
Managment Potential ....................................................................................................................13
Shoreline ..........................................................................................................................................13
Managment Potential .....................................................................................................................15
Riparian ............................................................................................................................................15
Managment Potential .....................................................................................................................18
Upland ..............................................................................................................................................19
Managment Potential .....................................................................................................................21
Public Use .......................................................................................................................................................22
Literature Cited ..............................................................................................................................................23
Appendix A. Potential information needs that may be required to address the recommendations
provided in the evaluation section ..................................................................................................................27
Appendix B. Scientific and common names of animals and plants known to occur on Kirwin NWR.
Information on fish, amphibians, and reptiles obtained from Kansas Department of Wildlife and
Parks (refuge files dated 01/30/2003) ..............................................................................................................29
Appendix C. Total annual use days, average annual populations, and peak populations, respectively
for the following waterfowl groups using Kirwin National Wildlife Refuge between 1983 and 2001:
American Coot and dabbling ducks excluding Mallard (a – c), diving ducks (d – f), Canada Goose
and Mallard (g – i), and White-fronted Goose and Snow Goose (j – k). .......................................................33
Appendix D. Conservation status for avian species based on regional and national plans ...................... 39
1
Summary
This report represents an initial biological
assessment of Kirwin National Wildlife Refuge
(NWR) conducted as part of the pre-planning phase
for development of a Comprehensive Conservation
Plan (CCP). Stimulation for the report was based on
the concept that future decisions related to the
biological portion of the CCP will be based on the best
available science. Therefore, an attempt is made to
integrate information from many different scientific
disciplines (e.g., geology, hydrology, biology) to help
identify ecological constraints and opportunities
imposed by the land base being considered.
Consequently, there is a greater likelihood of
identifying potential shortcomings of various
management actions during the decision making
process.
Information in this report is based on a relatively
limited number of published articles, past notes, and
observations. An attempt was made to locate
sufficient relevant information necessary to formulate
more definitive ideas and provide additional context.
Thus, the information provided below is known to be
incomplete and a more thorough synthesis will be
required. Further, interpretation of published
information can vary among individuals and the refuge
staff is encouraged to review the documents cited in
this report. Their years of observation and experience
managing the refuge are invaluable to ensuring that
information used to make decisions is applicable.
Consequently, some sections contain information that
was not fully explored in the evaluation section;
however, it was retained because it may be useful as
the refuge staff and core CCP team examines
different management options. Finally, decisions
regarding management of each individual community
should be combined and evaluated collectively to
identify potential conflicts. Although this may seem
simple and straightforward, this task often is difficult
because it frequently requires an iterative approach to
ensure that important issues have not been omitted.
This report does not contain conclusions, nor does it
advocate any opinions (favorable or unfavorable)
regarding the biological program. Further, concepts
such as alternatives, goals, and objectives, are not
discussed. The core CCP team will address these
topics. Rather, it represents a summary that
hopefully will be used to focus future discussion
regarding biological data needs and approaches for
using this information to make decisions. Ultimately,
however, scientific information alone will not lead to a
definitive decision regarding future direction, because
biology is only one of many components that must be
considered in the evaluation. Therefore, it is
recommended that U. S. Fish and Wildlife Service
(FWS) personnel responsible for determining the
future direction of the refuge be consulted to establish
guidelines and agree on the approach that will be used
in evaluating the biological program prior to
proceeding.
2
Acknowledgments
Prior to writing the report, the author was invited to
the refuge for a two-day meeting with Erich Gilbert
(refuge manager), Craig Mowry (assistant refuge
manager), and Wayne King (regional refuge biologist).
The purpose was to become familiar with the site,
discuss management opportunities and constraints,
and identify potential types of information that would
assist the staff in developing a credible biological plan
to guide future management. These individuals
contributed significant time and insight regarding
management of the refuge. The assistance of Rachel
Lambhan and Mark Fly in locating and processing
information used in this report is greatly appreciated.
Thanks also to the following individuals for providing
reviews of an earlier draft: E. Gilbert, R. A. Gleason,
S. L. Jones, W. J. King, R.A. Laubhan, C. Mowry, D.
M. Mushet, and J. D. Petty.
3
Introduction
Stimulation for this report was generated by passage
of the 1997 National Wildlife Refuge System
Improvement Act (NWRSIA) that requires each
refuge in the National Wildlife Refuge System to
develop a CCP that includes goals and objectives that
are based on the best available science. To accomplish
this mandate, Region 6 of FWS contracted with the
Biological Resources Division of the U. S. Geological
Survey (USGS) to inspect refuge habitats and
synthesize available information pertinent to the
management of Kirwin NWR as part of a pre-planning
phase to guide development of a CCP. This report
represents such a synthesis.
The brevity of the site visit did not allow for detailed
discussions between USGS and FWS personnel, but it
did provide the opportunity to exchange thoughts
regarding the information needed to evaluate the
biological program. Thus, the ideas contained within
this report are of a general nature and should be
viewed as a collaborative effort that involved the
refuge staff. Additional work will be required to
objectively evaluate the biological program, and this
report should be viewed as an initial effort to start this
process. In addition, there are alternative ways of
approaching an evaluation that would require different
levels and types of information. Therefore, the
responsibility of FWS is to review the report and
other relevant materials, discuss available options
with appropriate personnel, and determine if the
identified information needs and recommendations
outlined in this report are acceptable and represent
the preferred manner of proceeding.
General descriptive information on refuge
establishment, topography, climate, geology, soils,
vegetation, and wildlife is intended to provide a brief
background of the refuge with regard to functions,
processes, and values. This information is important
as a baseline for understanding the impact of past
land alterations and for developing management
guidelines for the future. In contrast, the section on
conservation is intended to provide perspective
regarding potential refuge contributions to natural
resources based on conservation plans that have been
developed for application at larger geographic scales
that encompass the refuge. The section on evaluation
of community types discusses in more detail the
attributes of various communities that occur within
the refuge boundary. For ease of discussion, four
broad communities were delineated as follows: (1)
Reservoir Pool, (2) Shoreline, (3) Riparian, and (4)
Upland. For each community, a brief synopsis of
historic and current conditions is provided. Also,
potential management options are discussed along
with some associated benefits and detriments.
Appendix A summarizes the information needs that
may be required to address the recommendations
provided in the evaluation section. These
recommendations largely are those of the author and
are based on thoughts that resulted from discussions
with FWS personnel during the site visit trip in
March. Therefore, the list is incomplete from a
biological perspective and largely ignores recreational
and other considerations. Additional effort will be
required by FWS personnel to identify and integrate
issues, concerns, and recommendations through
internal discussions and public scoping. Although
some scoping has already occurred, hopefully this
report will assist future efforts by providing some
background biological information. Obviously, this
represents only the first step in a long process and
additional work is necessary.
4
Description
Refuge Establishment and Authorities
Kirwin NWR is an overlay project on a U. S. Bureau of
Reclamation (BOR) irrigation and flood control
reservoir known as Kirwin (U. S. Fish and Wildlife
Service, URL http://kirwin.fws.gov/refugemap.htm).
The reservoir was constructed before irrigation
became widely practiced (Christensen 1999).
Dedicated in 1955, the reservoir has a contributing
drainage area of 3,540 km2 (1,367 mi2) and a total water
storage capacity of 38,797 ha-m (314,550 ac-ft). The
storage capacity is allocated among flood control
(36.532 ha-m [215,115 ac-ft]), conservation storage
(11,057 ha-m [89,650 ac-ft]), and inactive or dead
storage (1,207 ha-m [9,785 ac-ft]) (Christensen 1999).
Kirwin NWR was established in 1954 pursuant to the
Fish and Wildlife Coordination Act (16 U.S.C. ¤ 664)
for the “…conservation, maintenance, and
management of wildlife, resources thereof, and its
habitat thereon,…” (U. S. Fish and Wildlife Service,
URL http://refuges.fws.gov/policymakers/). The
BOR owns the land and controls reservoir water
levels, whereas the refuge staff manages all other
activities on the land and water (U. S. Bureau of
Reclamation, URL http://www.usbr.gov/gp).
Location and Topography
The 4,366-ha (10,788 ac) refuge includes Kirwin
Reservoir and bordering areas in southeast Phillips
County, Kansas. Topography of the area is
characterized by rolling hills, the gently sloping
Kirwin terrace, and a narrow river valley formed by
the North Fork of the Solomon River (Leonard 1952,
Christensen 1999). The refuge encompasses portions
of the North Fork Solomon River and Bow Creek.
These rivers drain an area of 359,874 ha (889,248 ac)
above the reservoir (U.S. Bureau of Reclamation 2002).
The altitude of the terrace ranges from an elevation of
602 m (1,975 ft) in Phillips County to 445 m (1,460 ft) in
Mitchell County. The gradient of the North Fork
Solomon River channel is about 1.3 m/km (7.1 ft/mi) in
Phillips County.
The refuge is located in the North Fork Solomon
River Sub-Basin. The North Fork Solomon originates
in western Thomas County, Kansas, approximately
193 km (120 mi) west of Kirwin Dam and drains an
area of 3,556 km2 (1,373 mi2) (U.S. Bureau of
Reclamation 2002). Elevation of the area ranges from
about 430 m (1,410 ft) at the mouth of North Fork
Solomon River in Mitchell County, to about 640 m
(2,100 ft) in the western part of Phillips County. Like
other valleys in north-central Kansas, the North Fork
Solomon valley and its tributaries are asymmetrical
and typically have precipitous south walls and gently
sloping north walls. According to Leonard (1952) the
valley consists of broad undissected terraces and a
floodplain width that varies from 201-805 m (660-2,640
ft). The relief from the stream channel to the top of
the Kirwin terrace, which lies above flood level, is as
much as 12 m (40 ft). The Kirwin terrace slopes
gently (gradient = 1.4 m/km [7.3 ft/mile]), is
moderately well drained, and represents the primary
area of cultivated farmland. Historically, the elevation
of the floodplain varied between 4.6-7.6 m (15-25 ft)
below the Kirwin terrace and 3.7-4.9 m (12-16 ft) above
the water level of the river. Many of the ephemeral
streams that drain the uplands disappear on the
surface of the terrace, which suggests these streams
contribute a large part of their water to the
groundwater reservoir in the area.
Agriculture and ranching have been the primary
economic forces in the area since the early 1800’s (U.S.
Bureau of Reclamation 2002). In Phillips County, the
land in farms (220,398 ha [554,603 ac]) accounted for
97.8% of the county land base (229,478 ha [567,040 ac])
in 1997. Further, of the land in farms, cropland
(130,329 ha [322,043 ac]) accounted for 56.8% of the
county land base (U. S. Bureau of Reclamation 2002).
Representative crops produced in Phillips County
during 1997 included corn, sorghum, wheat, oats,
soybeans, and hay (U. S. Department of Agriculture
National Agricultural Statistics Services, URL http://
www.nass.usda.gov/census/census97/highlights/ks/
ksc074.txt).
The drainage area below the reservoir is 348,004 ha
(859,918 ac), of which 6,325 ha (1.8%; 15,630 ac) is
irrigated (Christensen 1999). The BOR operates
Kirwin Irrigation District Number 1 downstream
from the reservoir and provides surface water outflow
to irrigate as much as 4,650 ha (11,490 ac) of farmland
(U.S. Bureau of Reclamation 2002) that generally is
within 8 km (5 mi) of the North Fork Solomon River
(Christensen 1999). As mentioned previously, the
drainage area above the reservoir is 359,874 ha (889,248
ac), of which 24,525 ha (6.8%; 60,600 ac) is irrigated.
The use of surface water for irrigation first occurred
in 1928 with the establishment of two pumping plants,
but by 1946 a total 13 plants had been established
(Leonard 1952). Currently, the primary source of
irrigation water is from alluvial wells, which have
increased from <10 in 1949 to>150 in 1993 (U.S.
Bureau of Reclamation 2002).
The North Fork Solomon Sub-Basin is part of the
Solomon River Basin, which extends across parts of 17
Kansas counties and includes the Solomon River and
its major tributaries, the North Fork and South Fork
Solomon Rivers. The rivers and associated tributaries
drain approximately 17,716 km2 (6,840 mi2) of mainly
agricultural land (Christensen 1999). In addition to
Kirwin Reservoir, the BOR also operates two
additional reservoirs in the basin; Webster Reservoir
on the South Fork Solomon River and Waconda Lake
at the confluence of the North and South Fork
Solomon Rivers. The three reservoirs provide water
for irrigation, municipal, industrial, and domestic use;
flood control; recreation; and fish and wildlife habitat
(Christensen 1999).
The elevation of the basin varies from approximately
1,006 m (3,300 ft) in the west to 351 m (1,150 ft) in the
east near the town of Solomon, Kansas. The average
gradient of the region is approximately 2.7-2.8 m/km
(14-15 ft/mi). The average gradient for the main stem
123°
5
Solomon River is 0.9 m/km (5 ft/mi) (U.S. Bureau of
Reclamation 2002). Both the North Fork and South
Fork Solomon Rivers derive their flows from
precipitation runoff and groundwater discharge from
underlying aquifers (U.S. Bureau of Reclamation
2002).
Finally, the Solomon River Basin is located in both the
Smoky Hills and High Plains Physiographic Regions
of the Great Plains Physiographic Province
(Launchbaugh and Owensby 1978). The High Plains
region of Kansas extends from the western state line
eastward into Graham County. The topography is
characterized by flat to gently rolling hills with
narrow, shallow valleys of low relief. Sand, gravel, and
porous rock cover most of the region. The Smoky
Hills Region, which encompasses Kirwin NWR, is
composed of three distinct hill ranges. Steep chalk
bluffs characterize the western range of hills, whereas
Greenhorn Limestone and Dakota Sandstone cap the
middle and eastern range of hills, respectively. The
eastern boundary of the Smoky Hills Region is in Clay
County and is adjacent to the Flint Hills
Physiographic Region (Kansas Geological Survey,
URL http://www.kgs.ukans.edu/Physio/physio.html).
Vegetation communities within this region are
classified as mixed-grass prairie with forested river
bottoms (Kuchler 1974).
Climate
The climate of the Solomon Basin is classified as
subhumid. Summers are characterized by hot days
and cool evenings, whereas winters are normally
moderate with light snowfall and only occasional short
periods of severe cold. The average length of the
growing season is about 167 days (Leonard 1952) and
the frost-free period extends from 29 April to 13
October (Albertson 1937). Long-term climate data (5/
1/1952 – 12/31/2002) was obtained from the National
Climate Data Center cooperative station located at
Kirwin Dam (http://lwf.ncdc.noaa.gov/oa/climate/,
station # 144357). The mean monthly maximum
temperature ranged from 3.1 C(37.5°F) in January to
33.4°C (92.2°F) in July, whereas mean monthly
minimum temperature ranged from -11.3°C (11.6°F) in
January to 17.8 °C (64.0°F) in July.
Average annual precipitation during this period was
58.5 cm (23.0 in), with 44.2% of total annual
precipitation occurring in May (mean = 10.2 cm [4.0
in]), June (mean = 7.8 cm [3.1 in]), and July (mean =
7.7 cm [3.0 in]). However, not all of this moisture is
necessarily available for plant growth because
evaporation is also occurring during these months.
Graphs obtained from the National Oceanic and
Atmospheric Administration (URL http://
www.noaa.gov), which depict ranges of evaporation for
the entire U.S, were used to obtain a coarse estimate
of 28.2 cm (11.1 in) of annual evaporation for north-central
Kansas. Months with highest evaporative
losses were June (5.6 cm [2.2 in]), July (6.1 cm [2.4 in]),
and August (5.6 cm [2.2 in]).
The Palmer Drought Severity Index (PDSI) was
developed to represent the severity of dry and wet
periods based on monthly temperature and
precipitation data as well as the water holding
capacity of soils at a location (Palmer 1965). Thus, this
measure provides a method integrating the above
information. For north-central Kansas, the long-term
PDSI (1895-2002) indicates cyclic patterns of drought
and wetness. During 1989 and 1990, portions of 1991,
and for a brief period in 2001, this region experienced
severe drought, but from late 1993 through mid-1994
the area was extremely wet (National Climate Data
Center, URL http://lwf.ncdc.noaa.gov/oa/climate/).
Geology
The surface geology of the Solomon Basin consists of
unconsolidated and consolidated rocks. The
unconsolidated surface deposits consist of Quaternary
alluvium, loess, and the Tertiary Ogallala Formation,
whereas Cretaceous and Permian rocks form the
bedrock. In general, the basin is underlain by strata
of marine origin (Christensen 1999). The dendritic and
asymmetrical drainage pattern of the Solomon River
suggests the lack of faults and folds and the presence
of flat underlying rock units (U.S. Bureau of
Reclamation 1984).
The Greenhorn Limestone, Graneros Shale, and
Dakota Sandstone outcrop as far east as western Clay
County, Kansas. Permian beds outcrop in counties
farther east. The Greenhorn Limestone consists of
alternating beds of calcareous shale and chalky
limestone. The Graneros Shale is noncalcareous,
fissile shale with sandstone lenses. The Dakota
Formation consists of lenticular sandstone bodies that
are embedded in mudstone. Generally, the sandstones
are fine to medium grained, well sorted, and exhibit
cross-bedding (Kansas Department of Agriculture
Division of Water Resources), URL http://
www.accesskansas.org/kda/dwr/).
The North Fork Solomon River is underlain by, or
incised into, Cretaceous beds that generally dip to the
west, whereas the erosional surface generally slopes
to the east. The oldest subsurface rocks at the
eastern end of the basin are of the Sumner Group.
Above the Sumner Group is Cretaceous marine
sediment beginning with the Dakota Formation, which
is overlain by the Cheyenne Sandstone, Kiowa Shale,
Graneros Shale, Greenhorn Limestone, and Carlile
Shale. The Carlile Shale is exposed in stream valleys
in Phillips County. Above the Carlile Shale is the
Niobrara Formation, which is exposed in much of the
North Fork Solomon River Basin (Leonard 1952), and
the Pierre shale, of which there is only one known
small outcrop in the basin upstream from Webster
Reservoir (Moore and Landes 1937, Ross 1991). The
Pierre Shale lies conformably on the Niobrara Chalk,
which is a gray, shaly, fossiliferous chalk with
weathered surfaces. The chalk contains bentonite
beds and limonite concretions (Kansas Department of
Agriculture Division of Water Resources).
The north and south divides of the Solomon River are
capped by remnants of the Ogallala formation in the
western part of the Solomon Basin, whereas the
uplands and valley walls over much of north-central
6
Kansas are composed of loess of the Sanborn
formation that was deposited during glacial retreat
(Leonard 1952). The Ogallala formation was formed
during the Pliocene by eastward flowing streams that
filled pre-existing valleys with alluvial sediments.
Continued deposition of alluvial sediments formed a
broad alluvial plain. The Ogallala consists mainly of
silt, sand, gravel, and “mortar beds” formed by
cementation of sediments with calcium carbonate.
However, lenticular beds of well-sorted sand, gravel,
bentonite, and volcanic ash also exist. The Ogallala
lies unconformably on the Pierre Shale in the western
part of the basin and on the Niobrara Formation in the
eastern part of the basin. The surface of the Ogallala
dips to the east-northeast and the average gradient is
2.1 m/km (11 ft/mi) (Kansas Department of
Agriculture Division of Water Resources).
Narrow belts of alluvium, most of Recent age, are
adjacent to the Solomon River channel and its
tributaries and occupy the floodplain (Leonard 1952).
The alluvium consists mainly of gravel, sand, silt, and
some clay. However, loess also may occur along
major streams. The loess is underlain by stream-deposited
sands that are in a high terrace position
with respect to the valleys (Leonard 1952). At several
places in the floodplain, wind has deposited sand from
the alluvium into dunes or in thin layers that cover the
terrace surfaces (Leonard 1952). These areas of sand
deposition occur in Phillips County, but thickness of
the fluvial and loess deposits is < 3.0 m (10 ft) (Kansas
Department of Agriculture Division of Water
Resources). A map illustrating the locations of these
geologic features on the refuge was developed by
Johnson and Arbogast (1993) and can be obtained from
the Kansas Geological Survey (URL http://
www.kgs.ukans.edu/General/Geology/County/nop/
phillips.html).
Groundwater
The Sanborn formation, which consists of a thin layer
of loess that overlies Cretaceous rocks, is a locally
important source of groundwater (Leonard 1952). The
most important aquifer in the area, however, occurs in
the deposits underlying the Kirwin terrace surface.
In general, this terrace is underlain by 9.1-27.4 m (30-
90 ft) of unconsolidated deposits (e.g., coarse textured
sand and gravel) that is quite permeable and lies
below the water table (Leonard 1952). The broad,
nearly flat terrace surface constitutes a large
recharge area and streams that originate in nearby
hills contribute additional recharge. Groundwater
moves laterally through the terrace deposits and into
the alluvium or into the channel of North Fork
Solomon River. Thus, the water table in the Recent
alluvium is continuous with the water table in the
terrace deposits and with the water level in the
flowing streams. The coarse nature of the alluvium
makes it an important potential source of
groundwater (Leonard 1952). Hydraulic conductivity
has been estimated at 51.8 m/day (170 ft/day) with an
average transmissivity of 241.5 m2/day (2,600 ft2/day)
(Phillips 1980). Well yields vary from 38-1893 l/min
(10-500 gal/min).
The water table in the valley slopes from east to west,
and from the sides of the valley toward the center.
The downstream slope of the water table varies from
about 2.2 m/km (11.5 ft/mi) in western Phillips County
to about 1.2 m/km (6.4 ft/mi) near the town of Kirwin
(Leonard 1952). Most ephemeral streams in the area
are above the water table and, when flowing, probably
contribute some water to the groundwater. In
contrast, the Solomon River and Bow Creek are
gaining streams (e.g., flow in these streams is
partially maintained by groundwater that seeps into
the channel) (Leonard 1952).
Soils
In north-central Kansas, soils are composed primarily
of Mollisols in the suborder Ustolls. A dark surface
horizon rich in bases are primary characteristics of
Mollisols. Nearly all have a mollic epipedon, but
many also have an argillic, nitric, or calcic horizon.
Specifically, soils of the North Solomon Valley are
primarily fertile, silty clay loams derived from
reworked loess (Leonard 1952), some of which are rich
in selenium (U. S. Geological Survey, URL http://
ks.water.usgs.gov/Kansas/studies/ressed/). The soils
in valleys are slightly sloping, friable, and generally
have high agricultural productivity. In the western
and central parts of the basin, soils are generally
friable and relatively impermeable, with some silt
loam and loess. The more level soils in the western
and central parts of the basin are used for grain
cultivation and are moderately productive. The soils
in the eastern part of the basin range from shallow
sands to thick clays and generally have low
agricultural productivity (U.S. Bureau of Reclamation
1984).
Vegetation
Historically, the floodplains of both rivers supported
woody vegetation, tall grasses, and forbs, whereas the
uplands largely were mixed-grass prairie (Kuchler
1974). However, human settlement and associated
land use activities altered historic processes and,
ultimately, the plant and wildlife communities.
Although construction of the reservoir in 1952
represents an obvious perturbation that altered
various ecological aspects of the rivers and associated
floodplains, alteration of the uplands also occurred
prior to refuge establishment. The area surrounding
Kirwin NWR was cultivated extensively and also was
used to pasture cattle prior to 1945 (Leonard 1952).
The general location of these activities was related to
topography and soils. Much of the cultivation
occurred on the terrace due to the presence of fertile,
moderately well drained soils. In contrast, cattle
production typically occurred on areas bordering the
valley where cultivation was prevented because of
steep gradients or presence of rocky soil formed on
chalk and limestone rocks (Leonard 1952). Although a
detailed history of past land use was not developed for
the refuge, a study conducted by Rezsutek (1990)
supports this scenario. He reports that lands
composing the refuge were formerly family farms and
much of the native grassland in the area had been
turned under for the production of crops prior to
establishment. Further, although J. Launchbaugh (in
7
K. Launchbaugh’s field notes) described some areas
as “native prairie”, Rezsutek (1990) suggests they
may have been “restored prairie”.
Grassland, cropland, deepwater and shoreline habitats
of the reservoir, and riparian zones bordering the
tributary rivers are dominant communities on the
refuge. In addition, shelterbelts, palustrine wetlands,
and chalk bluffs also occur within the refuge
boundary. When the reservoir is at conservation pool
(527.1 m [1729.25 ft]) there are 2,050 ha (5,065 ac) of
surface water and about 60 km (37 mi) of shoreline.
According to refuge staff, croplands occupy about 486
ha (1,200 ac) at conservation pool. Remaining
community types encompass 1,826 ha (4,513 ac) at
conservation pool and include grasslands,
shelterbelts, and riparian habitat. However, the area
of each community was not available.
Of the community types on the refuge, the reservoir
(e.g., deepwater habitat) and associated shoreline,
cropland, and shelterbelts were not present prior to
human settlement. Consequently, the area of native
communities on the refuge has been reduced.
Further, the grassland and riparian communities,
although historically present, have been severely
altered floristically and structurally. For example,
two plant species that may occur on the refuge
(western prairie-fringed orchid and Meads milkweed;
scientific names of all species mentioned in this report
are given in Appendix B) are listed as threatened or
endangered under the Endangered Species Act (ESA)
of 1973 (16 U.S.C. 1531-1544, 87 Stat. 884; URL: http://
laws.fws.gov/lawsdigest/esact.html). More detailed
information is presented in the section entitled
Evaluation of Community Types.
8
The 1997 NWRSIA mandates that each refuge
develop a CCP that is consistent with the principles of
sound fish and wildlife management and available
science. Further, this act also specifies that each CCP
shall identify and describe the purposes of each
refuge; the distribution, migration patterns, and
abundance of fish, wildlife, and plant populations and
related habitats; significant problems that may
adversely affect the populations and habitats of fish,
wildlife, and plants and the actions necessary to
correct or mitigate such problems; and, to the
maximum extent practicable and consistent with this
Act, be consistent with fish and wildlife conservation
plans of the State in which the refuge is located.
The purpose of this report was not to fully develop
information on all species potentially occurring on the
refuge. However, some general future direction must
be specified with regard to wildlife given the purpose
for refuge establishment. Therefore, this report
concentrates on the importance of the refuge to
migratory birds because these species represent a
primary FWS responsibility according to the
requirements of the Migratory Bird Treaty Act of
1918 (16 USC 703-711; 40 Stat. 755; URL: http://
laws.fws.gov/lawsdigest/migtrea.html). This should
not be interpreted as meaning other vertebrates,
invertebrates (e.g., butterflies), and plants can be
ignored since these organisms are important as
individual entities and also because they are critical to
proper system function. Rather, information
regarding the habitat requirements of these species
also should be used in evaluating the direction of
future refuge management to ensure that valuable
opportunities are not overlooked.
Baseline information on the avian community of
Kirwin NWR was developed using a checklist of bird
species sighted on the refuge (Igl 1996). Scientific
names for all species mentioned are provided in
Appendix B; birds follow the American Ornithologists’
Union Committee on Classification and Nomenclature
(American Ornithologists’ Union 1998, 2000, 2002,
2003). In addition, refuge files of duck, goose, and
swan counts were used to generate graphs of total
annual use days, average annual populations, and
average peak populations spanning a 20-year period
(Appendix C). There are several qualifying factors
that must be considered when considering this
information. First, the list from the website
represents a composite of all birds that have been
sighted over a long time; thus, the list may not
accurately represent the current avian community.
Second, the list only designates occurrence; thus, the
contribution (e.g., source/sink) of the refuge to the
species population is not known. Although refuge
waterfowl counts contribute information on
abundance, it is difficult to compare data among years
with any certainty because routes and areas surveyed
are not available and likely have varied among years.
In addition, count information was not collected based
on community type or bird activity. Thus, it was not
possible to use this information to determine local use
patterns or assess relative importance of different
communities. Similarly, the avian list (Appendix B)
was not developed using standardized protocols and
methods, but based on the long-term refuge bird list,
with an additional 29 species added from a research
study conducted in the riparian zone on the refuge in
the mid-1990s (Sevigny 1998). Regardless of these
constraints, this list is valuable because it can help
focus discussion among individuals (e.g., FWS
personnel, core CCP team) responsible for
determining the future management direction of the
refuge.
Finally, depending on the source and type of
information sought, Kirwin NWR is located in many
different regions. In all cases, there is considerable
overlap among boundaries although the area
encompassed tends to vary greatly. To provide an
overall perspective, relevant information regarding
species of concern and population targets contained in
these plans has been summarized, but no attempt has
been made to prioritize or make decisions regarding
species or guilds that should receive attention. In
some cases, species considered to be of conservation
concern at a regional level may not be of concern at a
national level, or vice versa. Such differences do not
indicate discrepancies; rather, it suggests differences
in distribution and population status at different
geographical scales. However, the small size of the
refuge precludes providing quality habitat for all
species and decisions likely will be required to
evaluate tradeoffs in management approaches and for
development of detailed habitat objectives.
Kirwin National Wildlife Refuge
The refuge bird list includes 233 species, of which 45
are recorded as nesting and four (Piping Plover, Bald
Eagle, Whooping Crane, and Least Tern) are listed as
threatened or endangered under the ESA. Kirwin
NWR also is recognized as a globally Important Bird
Area (IBA) by the American Bird Conservancy (URL
http://www.abcbirds.org/iba/kansas.htm). The IBA
program, initiated by BirdLife International in
Europe during the mid-1980’s, was developed to
recognize and support sites of importance to birds.
Based on the criteria developed by BirdLife
International, an IBA must maintain and support one
or more of the following: (1) species of concern (e.g.,
threatened and endangered), (2) species with
restricted ranges, (3) species vulnerable because of
population concentration, and (4) species vulnerable
because they occur at high densities due to their
congregative behavior (Kushlan et al. 2002).
State of Kansas
Wildlife resources in the state of Kansas were
historically rich and varied. Circa 1865, it is estimated
that the Great Plains portion of Kansas supported as
many as 407 bird species, including about 178 breeding
species (Fleharty 1995). Fish and herpetofauna were
not as rich due to the paucity of water, but included 30
fish species, 13 amphibian species, and 46 species of
reptiles (Fleharty 1995). Although Kirwin NWR is
small relative to the geographic area of Kansas, the
historic communities composing the refuge likely
supported many species mentioned in earlier
Wildlife Conservation
9
accounts. Appendix B contains a list of animals and
plants known to occur on the refuge.
Bird Conservation Region
Kirwin NWR is located within the Central Mixed-grass
Prairie Bird Conservation Region (BCR 19), an
ecologically distinct region of 535,734 km2 (206,848 mi2)
with similar bird communities, habitats, and resource
management issues. The area encompassed by BCR
19 extends from the edge of shortgrass prairie on the
west to the beginning of tallgrass prairie to the east
and includes portions of Texas, Oklahoma, Kansas,
and Nebraska (North American Bird Conservation
Initiative, URL http://www.nabci-us.org/map.html).
Although large areas in this region have been
converted to agriculture, areas of high-quality
grassland (e.g., Nebraska Sandhills) still remain,
including some of the best habitat for the Greater
Prairie-Chicken and Henslow’s Sparrow, and
sandbars along the larger rivers host a large
percentage of the continent’s breeding Least Tern
population. The region also is a spring migration area
for the American Avocet, Semipalmated Sandpiper,
and Buff-breasted Sandpiper.
Birds of Conservation Concern
The Birds of Conservation Concern (BCC) is the most
recent effort to satisfy the 1988 amendment to the
Fish and Wildlife Conservation Act, which mandates
FWS to “identify species, subspecies, and populations
of all migratory nongame birds that, without
additional conservation actions, are likely to become
candidates for listing under the Endangered Species
Act of 1973” (U. S. Fish and Wildlife Service 2002).
The document provides species lists at three
geographic scales: national, FWS regions, and BCRs.
Species considered for inclusion include nongame
birds, game birds without hunting seasons, and
numerous categories (candidate, proposed endangered
or threatened, and recently delisted) used in the ESA.
Parameters considered in determining if species
within these categories are of concern include
population size, extent of range, threats to habitat,
and other factors. The BCC should be consulted for
details regarding the assessment process.
There are 28 species known to occur on Kirwin NWR
that are considered to be of national conservation
concern in the BCC (U. S. Fish and Wildlife Service
2002). Among these are 8 shorebirds, 5 hawks and
falcons, 2 owls, and 2 sparrows. Twenty-one of these
28 species also are considered to be of conservation
concern at either FWS Region 6 or BCR 19 scale
(Appendix D). Special note should be made that some
species of conservation concern listed for BCR 19 are
not on the regional list and, likewise, several species of
regional conservation concern were not included in the
BCC list for BCR 19 (Appendix D).
North American Waterfowl Management Plan
The national goals set forth in the 1998 update of
North American Waterfowl Management Plan
(NAWMP) includes (1) maintaining the diversity of
duck species throughout North America and achieving
a mid-continent breeding population of 39 million
ducks during years with average environmental
conditions, and (2) reaching or exceeding mid-continent
populations for ten individual species,
including Gadwall, American Wigeon, Mallard, Blue-winged
and Cinnamon Teal, Northern Shoveler,
Northern Pintail, Green-winged Teal, Canvasback,
Redhead, and Greater and Lesser scaup. These
target populations are presented in Appendix D. The
plan also establishes population objectives for 30
populations of six goose species, three populations of
Trumpeter Swans, and two populations of Tundra
Swans. Of these, relevant objectives applicable to
Kirwin NWR include reducing all five populations of
Canada Geese that migrate through the central
flyway and also reducing mid-continent populations of
the Snow and Greater White-fronted geese to 1,000,000
and 600,000, respectively. The plan also sets forth
objectives to increase the interior population of
Trumpeter Swans to 2,500 and reduce the eastern
population of Tundra Swans to 80,000 (Appendix D).
Partner’s In Flight North American Landbird
Conservation Plan
The North American Landbird Conservation Plan
(NALCP) is a synthesis of priorities to guide national
and international conservation actions targeting 448
native landbirds from 45 families that breed in the
United States and Canada (Rich et al. 2004). Each
species is assigned scores ranging from 1 (low
vulnerability) to 5 (high vulnerability) for 6 factors
(population size, breeding distribution, nonbreeding
distribution, threats to breeding, threats to
nonbreeding, and population trend). These scores
subsequently are used to calculate a combined score
that represents relative conservation importance
(range = 4 [low concern] to 20 [high concern]).
Species with a combined score > 14, or combined
score = 13 and population trend score = 5, are
assigned to the Watch List that includes species of
highest conservation concern. In addition, a
Stewardship List was developed based on avifaunal
biomes in North America. These biomes were
delineated using cluster analyses to identify groups of
BCRs that share similar avifaunas. For each biome,
Stewardship Species are those species that have a
proportionately high percentage of their world
population within a single region during either the
breeding or wintering season. Kirwin NWR occurs in
the Prairie Avifaunal Biome, which is composed of
BCRs 11, 17-19, and 21-23 (Rich et al. 2004). The
NALCP should be consulted for details on the scoring
and assignment process, national and regional
population objectives, and other pertinent information
(Rich et al. 2004, URL http://
www.partnersinflight.org, URL http://www.rmbo.org/
pif/pifdb.html).
The Watch List and Stewardship List of continentally
important species in the United States and Canada
currently include 100 and 158 species (66 of these
species also occur on the Watch List), respectively
(Rich et al. 2004). Of these species, two (Greater
Prairie-Chicken, Dickcissel) of the Watch List species
and five (Mississippi Kite, American Tree Sparrow,
Lark Bunting, Grasshopper Sparrow, and Chestnut-
10
the Prairie Avifaunal Biome, respectively. Of these,
two species (Greater Prairie-Chicken and Dickcissel)
on the Watch List and six species (Mississippi Kite,
American Tree Sparrow, Lark Bunting, Grasshopper
Sparrow, Chestnut-collared Longspur, and Lapland
Longspur) on the Stewardship List are known to
occur on Kirwin NWR.
Shorebird Conservation Region
Kirwin NWR is located in the Central Plains/Playa
Lakes Region (CP/PLR) (United States Shorebird
Conservation Plan, URL http://
shorebirdplan.fws.gov/RegionalShorebird/
RegionsMap.asp). This region is larger than the area
encompassed by BCR 19 and includes portions of
Texas, eastern New Mexico and Colorado, western
Oklahoma, Kansas, Nebraska, and southeast
Wyoming. Thirty-eight shorebird species use habitat
in the CP/PLR during migration and 13 of these
species also breed in the region (Fellows et al. 2001).
Of these, 16 species have been identified as species of
primary concern. Based on the Kirwin NWR bird list,
13 of these priority species have been documented on
the refuge, including Snowy Plover, Long-billed
Curlew, Upland Sandpiper, White-rumped Sandpiper,
Baird’s Sandpiper, and Piping Plover (Appendix D).
The national and regional plans should be consulted
for national population objectives, justifications for
species designations, and other pertinent information
(U. S. Shorebird Conservation Plan, URL http://
shorebirdplan.fws.gov/RegionalShorebird/downloads/
CPPLR.doc).
Waterbird Conservation Region
Kirwin NWR is within the Central Prairies Region of
The North American Waterbird Conservation Plan
(NAWCP). In North America, separate initiatives
exist for waterbirds, shorebirds, and waterfowl.
Thus, the NAWCP focuses on seabirds, coastal
waterbirds, wading birds, and marsh birds (Waterbird
Conservation for the Americas, URL http://
www.waterbirdconservation.org/waterbirds/). There
are 23 species listed in the Central Prairies that have
been documented on Kirwin NWR. Of these, the
conservation status of six species are designated as
“not currently at risk”, five are considered of “low
conservation concern”, nine are of “moderate
conservation concern”, and three are of “high
conservation concern” (Kushlan et al. 2002; Appendix
D). The entire plan should be consulted to fully
understand how scores were determined.
Playa Lakes Joint Venture
At a smaller geographic scale, Kirwin NWR is part of
the Playa Lakes Joint Venture (PLJV; URL http://
www.pljv.org/about01.html), which encompasses most
of BCR 18 (Shortgrass Prairie) and BCR 19 (Central
Mixed-Grass Prairie). Joint ventures originally were
conceived by FWS in 1986 to implement the NAWMP.
URL http://northamerican.fws.gov/NAWMP/
nawmphp.htm). However, in addition to waterfowl,
many joint ventures (including the PLJV) are now
incorporating an “all bird” approach. National and
international bird plans provide the foundation for the
PLJV master plan, which sets direction for
conservation activities within the region. Established
in 1989, the mission of the PLJV is to create
sustainable landscapes for the benefit of birds, other
wildlife, and humans. More specifically, the PLJV
directs effort to restore, preserve and protect myriad
habitats, including playas, saline lakes, riparian areas,
and grasslands for resident, wintering, migrating, and
breeding birds. More than 400 species of birds use the
PLJV, including continentally important populations
of waterfowl, shorebirds, other waterbirds, and
grassland birds. The objectives established for the
PLJV in the 1998 update to the NAWMP are to
restore and enhance 4,047 ha (10,000 ac) and 10,117 ha
(25,000 ac) of habitat, respectively, and protect 20,639
ha (51,000 ac) of existing habitat.
collared Longspur) of the Stewardship list species are
known to occur on Kirwin NWR (Appendix D). In
contrast, there are 21 and seven species of continental
importance on the Watch List and Stewardship List in
11
This section has been divided based on general
community designations. This was done to improve
clarity, but it should be recognized that such
distinctions are arbitrary. Communities do not occur
as distinct entities but grade together as evidenced by
the movement of nutrients, energy, and wildlife within
and among communities. Therefore, information for
one community may be relevant for other
communities. Attempts were made to identify these
relationships, but some may have been overlooked.
For each community, a brief history is provided on
historic and current conditions and potential concerns
and opportunities are identified. The inclusion of
historic information is not intended as an effort to
direct refuge management toward restoring
presettlement conditions. Rather, historic
descriptions have been incorporated because they can
provide valuable insight regarding the original
location, extent, and vegetation composition of
communities and changes in abiotic factors (e.g.,
hydrology) that have occurred through time.
Together with information on current conditions,
historic descriptions can be used to (1) identify
important changes in processes that may require
further evaluation and (2) better understand the
potential of refuge lands.
Reservoir (Deepwater)
Historically, there was no deepwater habitat on the
area that now constitutes the refuge. Flows from the
North Fork Solomon River and Bow Creek flowed
unimpeded through refuge lands and occasionally
inundated the floodplain during wet periods.
Construction of Kirwin Reservoir has changed these
conditions. Obviously, damming the flows of the
Solomon River and Bow Creek and impounding water
in the historic floodplain of the rivers created
deepwater habitat. The surface acreage of the
reservoir varies dramatically from about 2,024 ha
(5,000 ac) at conservation pool (527.7 m [1731.25 ft]
elevation) to 356 ha (879 ac) during drought periods
(refuge staff). During the site visit the reservoir
elevation was 522.9 m (1715.6 ft), but water is expected
to drop an additional 3.4 m (11 ft) in the summer of
2003 (refuge staff). These fluctuations likely are due
to a combination of frequent drought periods coupled
with upstream pumping from the aquifer (U.S. Bureau
of Reclamation 2002). Since the mid-1960’s, inflows to
Kirwin Reservoir have declined significantly as
evidenced by a long-term reduction in average annual
inflow of 3,577 ha-m (29,000 ac-ft) between 1920-1964
(6,562 ha-m [53,200 ac-ft]) and 1965-1999 (4,070 ha-m
[33,000 ac-ft]; U.S. Bureau of Reclamation 2002). In
addition, >150 alluvial wells occur above the refuge
(U.S. Bureau of Reclamation 2002). The majority of
these wells are for agricultural uses, but municipal
wells also exist.
There also have been less obvious influences. Prior to
settlement, some amount of sediment was
transported from the uplands to the channel during
storm events. The amount of sediment varied, but
intact upland and floodplain vegetation probably
reduced the amount of sediment that entered the
channel. Following settlement, increased agricultural
activity likely altered the amount and pattern of
sediment transport and deposition in the valley. More
than 50% of the basin is currently cropland (U.S.
Bureau of Reclamation 1984) and cultivation and
intensive grazing in some areas (e.g., areas with large
topographic relief) have likely increased the amount of
erosion, and therefore sediment, entering the
floodplain. Prior to constructing reservoirs in the
Solomon Basin, the distribution of this sediment
varied depending on antecedent conditions and
magnitude of the current event. Following
construction, however, the dams functioned as a
barrier to sediment transport downstream. Thus,
although sediment deposition can occur at various
locations upstream of Kirwin Dam, the dam itself now
represents a terminal location that likely traps the
majority of sediment that enters the reservoir.
The potential impacts of increased sedimentation at
one location are numerous. In terms of quantity,
sediment is the major pollutant of wetlands, lakes,
estuaries, and reservoirs in the United States (Baker
1992). Sediment quality also is an environmental
concern because sediment may act as both a sink and
source for water-quality constituents (U. S. Geological
Survey, URL http://ks.water.usgs.gov/Kansas/
studies/ressed/). Once in the food chain, sediment-derived
constituents may bioaccumulate and pose an
even greater concern to fish, wildlife, and humans. In
addition, sediment loads may never consolidate with
bottom materials. The surface waters in the basin of
the North Fork Solomon River are reported as turbid
with moderate to high concentrations of dissolved
solids (U.S. Bureau of Reclamation 2002). Thus,
increased sedimentation may increase turbidity even
more due to wind and wave action that periodically
suspends sediment throughout the water column.
This could lead to other impacts, including reduced
dissolved oxygen concentrations, altered nutrient
availability, and reduced sunlight penetration. If
sufficient, these changes can eliminate or reduce
growth of submerged aquatic vegetation (SAV) (Robel
1961, Kullberg 1974, Dieter 1990).
The extent that sediment impacts have occurred, or
potentially could occur, in Kirwin Reservoir has
received attention recently. In 1998, the BOR initiated
a sampling program to assess the presence or absence
of organic and inorganic compounds in reservoir
waters. Part of this study involved collecting two
groups of four sediment cores near the dam
(Christensen 1999). Sediment thickness estimated
from these cores ranged from 2.9-3.4 m (9.5-11.3 ft) in
the first group of 4 cores to 2.1-2.3 m (6.9-7.4 ft) in the
second group. Unfortunately, it was not possible to
accurately determine sedimentation rates due to core
shortening (i.e., essentially a partial collapse or
compression of the core that prevented accurate
dating). However, a visual examination of the cores
revealed thick layers of sediment in the deepest
Community Types
12
intervals, which indicates sediment deposition was
greater in the early years of the reservoir. This is
consistent with other reservoir studies (Ritchie et al.
1986; Callendar and Robbins 1993) that have
demonstrated decreased sedimentation rates with
reservoir age. Historical stream flow data indicate
that much of the early sediment deposition in the
reservoir may have been caused by floods during the
1957 and 1960 water years (Christensen 1999).
Another objective of the BOR sampling program was
to determine potential environmental effects due to
elevated levels of total organic carbon (TOC), trace
metals, and major nutrients. The Environmental
Protection Agency has established two threshold
concentrations for many of these elements. The
threshold effect level (TEL) is assumed to represent
the concentration below which toxic effects rarely
occur, whereas the probable effect level (PEL)
indicates the concentration that usually or frequently
results in toxicity. Adverse effects occasionally occur
at concentrations between the TEL and PEL. Both
the TEL and PEL are guidelines used to screen for
possible hazardous chemical levels, but are not
regulatory criteria.
Total organic carbon was measured because various
organic solutes can form complexes that affect metal
solubility (Hem 1992). The median TOC concentration
in the reservoir was 11,600 mg/kg and the trend was
not increasing. There are no published TEL and PEL
limits for TOC; thus, the impact of existing levels is
not readily apparent. However, further investigation
should be conducted to obtain information from other
reservoir studies to ascertain potential impacts of
current TOC levels.
Selenium (Se) is a naturally occurring trace element
common in the marine shales underlying the Solomon
River Basin (see section on Geology). This metal is of
concern because irrigation in other areas underlain by
marine shales has resulted in elevated Se
concentrations that have caused birth defects,
reproductive failure, and death in fish and wildlife (U.S.
Bureau of Reclamation 2002). No TEL or PEL has
been established for Se, but concentrations >4.0 mg/
kg in sediment can result in bioaccumulation in fish
and wildlife (Lemly and Smith 1987). Concentrations
of Se in Kirwin Reservoir bottom-sediment ranged
from <0.3 to 2.2 mg/kg, indicating low potential for
bioaccumulation (Christensen 1999). However, Se did
exhibit a significant increasing trend (P = 0.006) in one
of the two cores, suggesting that concentrations may
be of concern in the future.
Reports by Christensen (1999) and Christensen and
Juracek (2001) also indicate median arsenic (As)
concentrations (range = 4.6-10.0 mg/kg) exceeded the
TEL (7.24 mg/kg) but not the PEL (41.6 mg/kg)
established for this element. However, a significant
increasing As trend was not evident. Arsenic could
originate from many potential sources, including
underlying geologic features (Christensen and Juracek
2001) or pesticides and industrial activities (Pais and
Jones 1997). However, industrial sources are not likely
given the predominance of agriculture in the basin
(Christensen and Juracek 2001). The median
concentration of copper also exceeded the TEL (18.7
mg/kg) as did cadmium in four samples. In contrast,
chromium, lead, nickel, silver, zinc, and mercury
either were not detected or did not exceed TEL limits.
These results clearly indicate that subsequent
monitoring of heavy metals and other water quality
parameters are warranted. Although no significant
effects have been documented, potential for future
issues may arise given evidence of increasing trends
for some metals.
Phosphorous (P) and nitrogen (N) are nutrients
required for plant growth, but excessive amounts can
enter reservoirs from fertilizer runoff or other non-point
pollution sources and create problems. The
median P and N concentration in core samples from
Kirwin was 616 mg/kg and 1,700 mg/kg, respectively.
However, only P exhibited a significant increasing
trend. Although no TEL and PEL limits have been
established for P and N, additional information could
be obtained to better understand potential impacts.
For example, excessive P has been shown to cause
algal blooms that can reduce dissolved oxygen
concentrations and cause fish mortality, or reduce
light penetration to levels that prevent growth of
some aquatic plant species. Information regarding
nutrient levels that result in algal blooms, or cause
other changes in aquatic biota (e.g., plants, animal)
could be used to develop desired thresholds.
Although reservoir water levels are managed by the
BOR, it may be possible for FWS to recommend or
help establish water quality criteria that would
ensure the needs of fish and wildlife are met.
Published information on the type and amount of SAV
in the reservoir was not located during the initial
literature search and the refuge staff was unable to
provide any qualitative observations. This is
unfortunate because plant composition and biomass
occurring in the deepwater community greatly
influences potential wildlife values. Plants capable of
growing in deep water provide substrate for
invertebrates (Krull 1970, Voigts 1976) that, in
combination with plant parts, provide foods for many
different vertebrates (e.g., fish, waterbirds). In
contrast, if SAV is not present, the deepwater
community may only provide roosting and loafing
habitat for birds. To better evaluate this community,
additional searches for information on plant resources
should be pursued, including contact with personnel
from Kansas Department of Wildlife and Parks and
BOR to obtain any reports or documents that may
exist.
Waterfowl counts conducted between 1983 and 2001
document ducks, geese, and swans occurring on the
refuge in varying numbers (Appendix C). On an
annual basis, the primary periods of use occur during
spring and fall migration; however, some species,
primarily Canada Geese and Mallards, remain on the
refuge during some winters (Appendix C, U.S. Bureau
of Reclamation 2002). Both diving ducks and geese use
the deepwater portion of the reservoir. Plant
13
composition and biomass information is lacking; thus,
it is not possible to determine if foraging habitat is
available. Waterfowl surveys only provide weekly
estimates on the entire refuge. Information on
numbers and activities (e.g., foraging, resting) of each
species in individual habitat types (e.g., deepwater
versus shoreline) are lacking. Therefore, this data
cannot be used to speculate on the type and
availability of resources and it is impossible to arrive
at any definitive conclusions. However, at a minimum
it is likely that the deepwater community provides
roosting and loafing habitat for waterfowl (ducks,
geese, swans), as well as sanctuary from shooting
during hunting season (U.S. Bureau of Reclamation
2002). This zone also could provide additional benefits
in the form of foraging habitat if SAV beds or
invertebrates are present. The types of foraging
habitat available would largely depend on the types
and locations of food items. For example, the
presence of pondweed drupelets or invertebrates
within about 46 cm (18 in) of the water surface is
available for dabbling ducks, whereas swans can
access pondweed foliage at greater depths
(Fredrickson and Reid 1986, Fredrickson and Laubhan
1994).
Based on conversations with refuge staff, another
interesting issue that would merit further
investigation is the value of the deepwater zone as
refuge during the hunting season. Currently, this
area is closed to hunting and the staff thinks this
increases the number and duration of time that geese
are in the area. A competing idea is that goose
numbers near the refuge are positively correlated
with the amount of row crops. Sufficient data may be
available to conduct a correlation analysis between the
size and availability of the closed zone, cropland acres,
and goose numbers. Although correlation analysis is
only a “measure of association” and does not prove
cause-and-effect, this analysis may provide some
insight or help identify variables to monitor in the
future.
Management Potential -The ability of FWS to
manage the deepwater habitat is minimal. Reservoir
elevations are determined by other federal entities
that must consider several factors (e.g., irrigation,
flood control) other than wildlife. Hydrology,
including the direction, magnitude, and time of water
level fluctuations, is the primary factor influencing
resource production and availability (Mitsch and
Gosselink 1993, Fredrickson and Laubhan 1994). The
inability of FWS to influence these hydrologic
parameters prevents the ability to reliably stimulate
or maintain desired plant communities and associated
food resources, or influence resource availability (e.g.,
water depth between food resources and water
surface). Even if FWS could establish guidelines
specifically for wildlife, the dramatic fluctuations in
surface area caused by uncontrollable factors (e.g.,
precipitation, upstream groundwater pumping) would
make it difficult to reliably and consistently achieve
desired outcomes.
Although direct management is minimal, the
deepwater community still provides resources that
contribute to the overall value of the refuge.
Therefore, FWS should consider options that can be
used to indirectly influence the values that are
provided as a result of annual reservoir operation.
Potential options to consider include working
cooperatively with BOR to establish water quality
criteria and continuing to maintain existing
agreements that designate a portion of the deepwater
community as a closed area during hunting.
Shoreline
The shoreline and deepwater communities are both
part of the reservoir and, therefore, are functionally
connected both spatially and temporally. They also
share some of the same ecological attributes,
including source and quality of water. However, these
communities have been separated because they are
very different with respect to some hydrologic
parameters (e.g., water depth), plant communities,
and wildlife resources.
Definitions vary, but the shoreline community is
defined in this report as the portion of the reservoir
(excluding the riparian zone) with water depths that
range from saturated soils to <61 cm (24 in). The
general shape of the shoreline is linear, but the width,
and spatial position of this area change both annually
and seasonally depending on reservoir water levels
and bathymetry (i.e., topography of reservoir bottom
sediments). For example, the bathymetry of the
shoreline has been differentially influenced by erosion
following reservoir impoundment. The presence of
deep and shallow cutbacks caused by wave action can
significantly influence habitat suitability for some
species that tolerate a narrow range of water depths
(e.g., shorebirds). The paucity of palustrine wetlands
on the refuge means that the shoreline is the only
community that potentially can provide substantial
foraging habitat for dabbling ducks (unless SAV
occurs in the deepwater community), shorebirds, and
wading birds. However, a sufficient area of suitable
(e.g., proper substrate, water depth) shoreline must
be available if the community is to provide limiting
resources (aquatic invertebrates, seeds, tubers) in
quantities that benefit different waterbird guilds.
Although area estimates of the shoreline community
were not available, the bathymetry and water level
data needed to develop estimates is likely available
from the BOR. The use of this data to develop curves
for estimating shoreline area is highly recommended
because it would likely prove useful in future
discussions regarding management potential and
values of this community. For example, the range of
water depths along the shore at different elevations
could be compared to water depths used by foraging
waterbirds to determine area of suitable habitat
available. In addition, the refuge staff reported that
an agreement exists between certain entities to
maintain conservation pool at 527.7 m (1731.30 ft),
rather than the legal elevation of 527.1 m (1729.25 ft).
The potential impacts (positive or negative) of this
increase on available foraging habitat for various avian
guilds could be estimated using the above mentioned
curves, but would be difficult otherwise.
14
Because area is important, a coarse estimate of 91-271
ha (224-670 ac) for the shoreline community at
conservation pool was derived to provide some
perspective. The accuracy of this estimate should be
viewed with extreme skepticism for several reasons.
First, the estimate uses an assumed average width of
15-46 m (50-150 ft). Exact widths are unknown and
likely vary extensively around the perimeter of the
reservoir. Second, the estimate is based on a shoreline
length of 60 km (37 mi) at conservation pool which
likely includes portions of the shoreline that would be
more appropriately considered the riparian
community. Also, and perhaps most important,
fluctuations in the reservoir surface are known to be
dramatic. Consequently, a single estimate at
conservation pool does not capture the full range of
shoreline area that occurs within and among years.
However, this estimate does suggest that the area of
shoreline is sufficient to warrant further
consideration.
The shoreline potentially can provide unique
resources for a diverse array of avifauna. According
to refuge files, Double-crested Cormorants and Great
Blue Herons have nested on the refuge since 1952 and
1963, respectively. Reproductive effort varies
annually, but between 1960 and 1995 the number of
Great Blue Heron nests has ranged from 1-20 with
production of 2-90 young. During the same period,
Double-crested Cormorant nests and young have
ranged from 3-37 and 40-60, respectively. The current
location of rookeries occurs within, or adjacent to, the
shoreline community near the main reservoir body in
the eastern portion of the refuge. Trees currently
used for nesting appear to be adjacent to stream
channels that were inundated when water was
impounded by the reservoir. Many of these trees were
killed as a result of high water in the 1990’s, but many
remain standing and still provide suitable nesting
habitat.
In addition, Least Terns occasionally nest within the
shoreline community and protection of ground nests is
required. Exposed sandbars constitute the preferred
nesting substrate of Least Terns. However,
substrates similar to sandbars are exposed along the
shoreline when reservoir elevation recedes and some
Least Terns occasionally nest in these areas.
The primary value of the shoreline community, based
on the geographic location of the refuge, likely is
foraging habitat for a variety of waterbirds. This area
constitutes a zone of high biological productivity. The
growth of plants during drawdown results in the
production of food resources (e.g., seeds, tubers) and
the release of nutrients when vegetation decomposes
upon reflooding can be assimilated by small aquatic
organisms (e.g., microinvertebrates) (Fredrickson and
Laubhan 1994). These organisms constitute the
forage base for macroinvertebrates, fish, and
amphibians, which are the primary foods of many
waterbirds. In addition, the hydrologic fluctuations
that occur within this area create numerous
microhabitats that can be used by numerous species.
Herons and other wading birds forage primarily on
aquatic animals, including fish, amphibians, and
macroinvertebrates. Although some species are
capable of capturing prey in water >60 cm (24 in), the
majority of foraging typically occurs within the
shoreline community (e.g., shallow water or along the
water-mud interface) (Fredrickson and Reid 1986).
Except for extreme fluctuations, changes in reservoir
levels likely do not alter production or availability of
fish, the primary food item of these species (but see
Gawlik 2002 for impacts that can occur given the right
circumstances). During drought years, it is
conceivable that fish kills may occur. This may or
may not impact foraging efficiency and nest success of
waders depending on the biomass of foods that remain
during these periods. Although pertinent data was
not located during this initial investigation, Kansas
Department of Wildlife and Parks may have relevant
information.
Ducks (diving and dabbling) and shorebirds also
forage within the shoreline community (Fredrickson
and Reid 1986, Skagen and Knopf 1994). In fact, the
paucity of palustrine wetlands suggests that these
species rely almost exclusively on the shoreline for
foraging when using the refuge. However, refuge
survey data does not provide information to confirm
this assumption. Further, the production and
availability of resources for these species is difficult to
predict because of the dynamic water fluctuations that
occur in this edge community. For example, during
March 2003 vegetation along the northern shoreline
included reed canary grass, saltcedar, and Canada
thistle. There also were extensive areas of bare
ground. Although the production of foods (browse,
seeds, tuber, etc.) for ducks and geese appears
minimal, the growing season had not yet started and
additional plants may germinate. If additional
germination does not occur, the extensive areas of
unvegetated shoreline likely will provide foraging
habitat for spring migrant shorebirds. However,
optimum foraging depths vary among shorebirds
depending on size (i.e., tarsus length); thus, not all
shorebirds would benefit equally. In contrast, a very
different plant community was evident during a field
visit to the refuge in 1999. This visit was conducted
during the growing season and water levels were
much higher. My field notes indicate minimal bare
ground and the presence of smartweed, millet,
bulrushes, cattail, beggarticks, ricecut grass,
spikerush, cocklebur, sedges, and panic grass among
other species. Depending on fall water conditions, the
shoreline would have provided excellent foraging
habitat for dabbling ducks and geese due to the large
biomass of seeds and browse produced. In contrast,
shorebird foraging habitat would likely have been
minimal due to excessive vegetation cover.
The above observations fromt two different years
provide evidence that the seed bank within the
shoreline community is diverse and includes both
desirable (e.g., browse, seed-bearing) and undesirable
(e.g., invasive, exotic) plant species. The species that
germinate from the seed bank, and the ultimate
densities of species that survive, are determined by a
multitude of factors. Most species that germinate in
15
the shoreline area require substrates that are moist
to wet, but not flooded (van der Valk and Davis 1978).
Thus, the most important factor controlling
germination likely is the annual changes in reservoir
water levels, including the magnitude, timing, and
rate of water level fluctuations. These hydrologic
parameters greatly influence recruitment from the
seed bank by affecting time of soil exposure, soil
temperature and oxygen levels, and the rate of soil
moisture loss (Leck 1989, Fredrickson 1991). Water
quality also may be important because constituents
(e.g., salts, iron, copper) in the water are bound by soil
particles at the soil-water interface and can affect
plant germination and growth. This deserves further
investigation because of water quality issues in the
reservoir. However, the diversity of plants that have
already been documented along the shoreline
suggests that water quality currently is not severely
impacting the germination or survival capability of
many species.
Management Potential – Similar to the deepwater
portion of the reservoir, the ability of FWS to manage
the shoreline community is constrained by the lack of
hydrologic control. Consequently, the value of the
shoreline community to waterbirds likely will vary
among species and years. Trees adjacent to the
reservoir and the presence of fish near the shoreline
are probably consistently available. Thus, suitable
habitat for breeding Great Blue Herons and Double-crested
Cormorants, as well as migrating and
wintering Bald Eagles, is usually present on the
refuge in most years. In contrast, foraging habitat for
ducks and shorebirds will be more variable for two
primary reasons. First, it is not possible to
manipulate water levels to match the germination
requirements of plants that produce a large biomass
of foods (e.g., seeds, tubers, browse) and provide
substrate for invertebrates. Second, water levels
cannot be intentionally manipulated to coincide with
duck and shorebird migration periods. Therefore, in
the absence of hydrologic control, some exposed and
vegetated shoreline habitat will be available to
shorebirds and ducks every year, but water level
changes that expose abundant foods during migration
will occur only sporadically. Finally, the availability of
habitat for Least Terns varies, but likely is more
predictable than ducks and shorebirds. This
statement is based on the reported long-term
drought/wet cycle of 30 years with about 23 years of
drought and seven years of wet conditions (refuge
staff). According to the refuge staff, reservoir pool
elevations tend to consistently decrease during the
drought phase. When this occurs, the availability of
substrates suitable for Least Tern nesting tends to
become more reliable, and the probability of nest
destruction due to flooding less likely, during a period
of several years. During the start of the wet period,
water levels in the reservoir start to increase,
available nesting habitat decreases, and, if nesting is
attempted, the likelihood of nests being destroyed by
flooding increases.
Another reality is the potential for an unfavorable
plant community to develop in the shoreline
community. The land-water interface in this zone is a
prime area for the establishment and proliferation of
many invasive species due to the frequent presence of
exposed soil, variable soil moisture, and high nutrient
availability. For example, along the north shoreline
numerous saltcedar seedlings and stems of Canada
thistle and reed canary grass were evident. Although
currently present only in small numbers, the
potential exists for expansion of these invasive species
(or others) along the shoreline, which could result in
the loss of current shoreline values (Sudbrock 1993,
Bailey et al. 2001). Evidence of this potential exists in
the floodplain of the lower riparian zone where reed
canary grass and Canada thistle currently dominate
the herbaceous vegetation (see below).
FWS cannot alter the hydrology of the reservoir to
minimize the potential for invasions of non-natives to
occur. Similarly, FWS cannot intentionally raise pool
elevation to eliminate invasions that do occur.
Nevertheless, the refuge staff is responsible for
addressing invasive species that do occur. Potential
control options (herbicides, fire, mechanical
equipment) exist, but implementation may not be
possible in some years (e.g., too wet). Also, many
techniques often are costly and require repeated
application to be successful. Thus, it is recommended
that decisions be made regarding the ability and/or
desire to conduct such operations under different
conditions. Information available in the literature and
refuge files should be adequate to develop working
hypotheses of potential tradeoffs (e.g., costs, benefits,
probability of success) related to active management
in this community. This information should be
consolidated prior to CCP development.
In summary, the shoreline community has the
potential to provide many values to waterbirds that
other communities on the refuge do not provide.
There also is potential for extensive, rapid colonization
of invasive species. These detrimental impacts are
common on many reservoirs, and approaches to
minimize impacts are often difficult to develop due to
constraints imposed by the reservoir operation plan.
In the case of Kirwin Reservoir, the only
recommendation is to consult with the BOR to
determine if annual operations can be altered slightly
to take advantage of existing conditions that occur in
some years. For example, it is likely that the release
of a relatively small volume of water in spring would
expose a large amount of shoreline habitat around the
reservoir for spring migrant shorebirds. Such
releases would not have to occur annually; rather, an
agreement could be developed that would result in
release only when pool elevations are above a certain
level. In many cases, such alterations may have only
negligible impacts on other reservoir uses but result
in significant wildlife benefits.
Riparian
The riparian community, which includes the floodplain
and channel of the Solomon River and Bow Creek, was
dynamic historically. Although both streams were
considered perennial (Leonard 1952), flows were
highly variable depending on precipitation cycles.
16
Stream hydrology was characterized by flood flows in
the spring and low flows or ponding during the
summer and fall (U.S. Bureau of Reclamation 2002).
These extremes in hydrology influenced the types of
flora that developed and the fauna that inhabited the
riparian system. During major floods the channel was
reworked, vegetation was uprooted, and sediment was
transported downstream and deposited at various
locations in the channel and floodplain. These actions
resulted in the creation of various channel habitats
(e.g., pools, riffles), marsh areas adjacent to the rivers,
and sites for regeneration and growth of various plant
types in the floodplain.
The historic floristic composition of the floodplain
included grasses, forbs, and woody vegetation.
Kuchler (1974) described this community as
“floodplain forest and savanna”, with scattered trees
and shrubs and a dominant ground cover of bluestem
prairie. However, he also states that “the prairie was
suppressed in areas of dense woody growth”,
suggesting that certain areas of the floodplain were
extensively forested. The wooded component
apparently was continuous but narrow based on
accounts of early settlers and one aerial photograph
(Plate 5, page 18 in Leonard 1952) of the Solomon
River near Glade, Kansas. Dominant woody species
included cottonwood, American elm, hackberry, and
peachleaved willow, whereas the dominant herbaceous
vegetation consisted of big bluestem, little bluestem,
switchgrass, and Indian grass. In contrast, marshes
were dominated by prairie cordgrass and lesser
numbers of myriad species, including bulrushes,
cattail, and rice cutgrass (Kuchler 1974).
The historic wildlife community inhabiting the
riparian community was diverse and unique. Forests
were rare in the Great Plains and the woody
vegetation provided cover, forage, and nesting
substrates for neotropical migrants that were not
available in other communities. The tall grasses
provided important resources for both migratory and
resident wildlife, and marshes provided resources for
a host of waterfowl. The stream fishery was not rich
and included only species (e.g., plains killifish, red
shiner, creek chub) that could tolerate extremes in
hydroperiod, temperature, current velocity, and
dissolved oxygen concentrations (U.S. Bureau of
Reclamation 2002).
However, as with other communities on the refuge,
human settlement and the accompanying changes
have greatly altered processes and influenced
vegetation in the riparian community. Among the
most important changes include reservoir
construction, increased groundwater pumping,
diversion dam construction, and irrigation canal
development (Christensen and Juracek 2001). The
potential range of impacts caused by these changes
varies from subtle to obvious depending on the year
and antecedent environmental conditions. The upper
portion of the riparian community differs greatly from
the lower portion due to the impacts of the above-mentioned
changes.
woody riparian vegetation on the Solomon River (3,112
ha [7,689 ac]) ranked second only to the Lower
Arkansas (5,083 ha [12,560 ac]) (Eddy 1994). The
composition of trees in the mid-1990’s was dominated
by eastern cottonwood (58%) and willow (25%) with
lesser amounts of American elm (4%) and green ash
(3%), hackberry, boxelder, and mulberry (Sevigny
1998, Eddy 1994). The shrub and vine component (5%)
also was evident, but some non-native trees have
invaded the system, including saltcedar (Eddy 1994),
Siberian elm, and honey locust (Sevigny 1998, refuge
staff). Perhaps the greatest change from historic
structure and composition has occurred in the ground
vegetation. The once dominant tall, warm season
grasses described by Kuchler (1974) have been
replaced by shorter cool season grasses (e.g., smooth
brome), which has altered structural and floristic
diversity (refuge staff, personal observation).
The avian community also remains diverse, which is
not surprising. The ability of riparian systems to
support a diverse assemblage of vertebrates is well
documented (Pashley et al. 2000). However, the
composition and relative abundance of species have
likely changed due to landscape level changes in land
use (e.g., agriculture). In 1997, a study of the riparian
bird community on the refuge during spring migration
resulted in the identification 87 species from 19
families (Sevigny 1998). A detailed inspection of this
list identified some intriguing (although not
substantiated) aspects that may be related to changes
in ground flora. The nine most abundant species
(>100 recorded) were the House Wren, Blue Jay,
Black-capped Chickadee, Mourning Dove, Northern
Cardinal, Common Yellowthroat, Red-winged
Blackbird, and Brown-headed Cowbird. Based on
Breeding Bird Survey (BBS) data for Region 6 of
FWS, the Black-capped Chickadee (n = 257 routes,
trend = 0.9, P = 0.19, 95% confidence interval [CI] = -
0.4 – 2.1), Mourning Dove (n = 568 routes, trend = 0.0,
P = 0.82, 95% CI = -0.4 – 0.5), Northern Cardinal (n =
73 routes, trend = 1.1, P = 0.06, 95% CI = 0.0 – 2.2),
Common Yellowthroat (n = 322 routes, trend = 0.1, P
= 0.89, 95% CI = -0.8 – 0.9), Red-winged Blackbird (n
= 525 routes, trend = 0.1, P = 0.84, 95% CI = -0.5 –
0.6), and Brown-headed Cowbird (n = 533 routes,
trend = 0.1, P = 0.71, 95% CI = -0.4 – 0.6) exhibited
stable populations trends, whereas the House Wren (n
= 410 routes, trend = 2.4, P = 0.00, 95% CI = 1.8 –
3.1) and Blue Jay (n = 179 routes, trend = 0.8, P =
0.02, 95% CI = 0.1 – 1.6), exhibited increasing
population trends between 1966 and 2003 (Sauer et al.
2004, URL http://www.mbr-pwrc.usgs.gov/bbs/
bbs.html). Further, most of these species are capable
of adapting to changes occurring in the riparian
communities throughout the western United States
(Saab 1999). In contrast, however, the list also
included 19 species whose status is of some concern
according to current regional and national plans
(Appendix D). The presence of these species in low
In the mid-1990’s, the floodplains of both streams
supported trees on the refuge, but the width varied
from a few scattered trees to areas as wide as 180 m
(590 ft) (Sevigny 1998). Of the nine river systems in
the western two-thirds of Kansas, the amount of
17
abundance suggests the riparian plant community has
not been completely altered, but subtle, significant
changes have occurred that has reduced habitat
suitability for some species. Additional investigation
to identify these changes and their causes would be
valuable for determining appropriate future
management actions. However, given the impacts of
high water during the mid-1990’s (see below) the
preceding statement only applies to the upper portion
of the riparian community.
Comparing shifts in avian communities between
historic and current periods often is used as a
technique to describe community changes. This
approach has much value, but it also has several
weaknesses. First, this technique cannot identify all
changes that potentially have occurred. Second,
changes in processes often can only be detected by
certain avian parameters (e.g., abundance, nest
density); thus, multiple parameters often must be
collected and this data is rarely available in historic
accounts. Finally, these comparisons only illustrate
past trends and do not identify cause-effect
relationships. Consequently, they provide little
information on future expectations, particularly in
environments that are subject to rapid and extreme
changes due to human events (see below).
To remedy this shortcoming, information regarding
change in processes that influence community
structure and function also must be developed.
Traditionally, ecologists assumed that the most
important processes affecting populations operated at
local spatial scales (Carothers et al. 1974, Urban and
Smith 1989). Recent research, however, has indicated
that larger scale assessment also should be
considered (Wiens 1989, Forman 1995). These large
scale assessments can help (1) identify changes that
are preventing desired conditions from being obtained,
(2) identify future management actions that are likely
to be most effective, and (3) determine if management
is feasible or warranted. Often, as is the case with the
riparian community, the evaluation largely is
subjective because all the required information is not
available. However, a combination of available
information integrated with logic and general
principles of how processes affect community
structure and function can still provide valuable
insight for making management decisions. The
following information has been developed based on this
perspective.
Increased groundwater pumping, canals, diversion
dams, and reservoir construction have all contributed
to altered stream flow in both streams (Christensen
and Juracek 2001). However, the impacts to the
riparian community caused by pumping, diversion
dams and canals differ in some ways from those
caused by the reservoir and will be discussed
separately. The first three activities occur above the
refuge, are associated largely with agriculture, and
have changed the annual hydrograph by reducing the
volume of water in the channel and changing the
timing of peak and low periods (Wis. Bureau of
Reclamation 2002).
Exact shifts should be determined by analyzing long-term
hydrographs (if available). However, compared
to historic conditions, the general effect is that larger
storm events or longer wet periods are required to
cause the same amount of overbank flooding and
channel scouring. The periodic occurrence of these
actions is critical to maintaining channel diversity
(e.g., pools, riffles) and creating conditions suitable for
germination of new woody and herbaceous vegetation.
In addition, the long-term average depth to the water
table underlying the floodplain has likely increased.
This change has occurred because the groundwater in
the floodplain is in direct connection with water in the
channel (see sections on Geology and Groundwater).
In general, these two entities are in dynamic
quilibrium. Due to upstream influences, the volume,
and therefore depth, of water in the channel has
decreased during non-flood periods. As water depth
has decreased, free water (i.e., not bound by soil
particles) in the ground has likely seeped into the
channel until equilibrium is reached or no more
groundwater is available. The greater the drop in
channel water depth (e.g., during extreme drought),
the more likely groundwater will seep into the
channel. Ultimately, these changes can result in
decreased soil moisture in the rooting zone of the
floodplain. This can impact plant community
composition and structure because altered soil
moisture can influence germination potential of seeds
and affect the growth of existing plants. Site-specific
information necessary to confirm these changes and
determine if the magnitude of change has been
sufficient to alter plant composition is not available,
but it is recommended that data be collected. This
can be accomplished by refuge staff using relatively
inexpensive methods and would be valuable in
determining future management actions.
Construction of the reservoir occurred immediately
downstream of the riparian community managed by
the refuge. Similar to upstream hydrologic
alterations, the dam has reduced flow velocity in the
stream because water no longer can be transported
downstream unobstructed. Historically, these events
were important because floodplain vegetation was
disturbed and areas suitable for new germination were
created. The reduced frequency or absence of these
events likely lowers the potential of bare, moist
substrate necessary for regeneration of species such
as cottonwood and willow (Scott et al. 1993). In
addition, the reservoir functions to store water during
wet years. During prolonged wet periods, or during
extreme precipitation events, the impoundment of
floodwaters can result in inundation of the floodplain
to deeper depths and for longer periods than
historically occurred. If inundation lasts a sufficient
time it can lead to the mortality of vegetation (Teskey
and Hinckley 1977). Also, the release of water from
the reservoir is timed to coincide with irrigation needs,
usually summer and early fall (U.S. Bureau of
Reclamation 2002). This, in combination with
upstream activities, has changed the period of
maximum stream flow from spring to summer. This
shift has several impacts, but one of the most
important is the potential effect on germination of
18
riparian vegetation. Seeds of many species, including
cottonwood and willow, are dispersed in spring, are
short-lived, and require bare, moist substrate for
germination. Thus, the shift from spring to summer
flows can negatively impact germination of these
species.
During certain years, or combinations of years, the
effect of these impacts can result in severe and long-lasting
effects on riparian vegetation. This is obvious
based on the damage to riparian vegetation caused by
the most recent wet period (1993-2000). This damage
was still evident in March 2003 and illustrates
potential management issues that should be
addressed during CCP development. A general
chronological description of events follows:
1. A period of high water starts in 1993 with a 140 cm
(55 in) rain event (U.S. Bureau of Reclamation 2002,
refuge staff). The riparian study (Sevigny 1998) was
being conducted at about this time.
2. Water levels in the reservoir increase enough to
back water into the lower portion of the riparian zone
immediately upstream of the reservoir.
3. The water remains at depths long enough in the
lower portion to kill all but 142 ha (350 ac) of riparian
vegetation (U. S. Fish and Wildlife Service 1996).
Although mortality was not as evident in the upper
riparian zone, it is likely that this area was also
impacted to some extent. For example, water in the
upper channel could not be evacuated downstream
until water was released from the reservoir. Thus,
some of the same plant species (e.g., reed canary
grass, Canada thistle) that became established in the
lower riparian zone also became established in low
elevation portions of the upper zone.
4. The wet period ends in 2000 and water recedes
between 2001 and 2003. To facilitate crop irrigation
downstream, releases occur primarily during summer
months (U.S. Bureau of Reclamation 2002).
5. The release of water is slow and scouring does not
occur in either the channel or floodplain.
6. Germination of woody vegetation is minimal
because bare, moist substrate is not available during
spring when seeds of cottonwood and willow disperse
from surviving parent trees.
7. Germination of herbaceous plants occurs, but
species composition is dominated by reed canary
grass and Canada thistle. This is expected since
seeds and rhizomes of these species are adapted to
growth in moist, warm soils that frequently occur
with summer removal of water.
8. In the spring of 2003, the floodplain consists of
standing, dead timber with an understory of Canada
thistle and reed canary grass.
This scenario likely occurs infrequently based on the
fact that it has occurred only once since reservoir
construction in 1952. This is not surprising based on
information provided by the refuge staff that the long-term
drought/wet cycle spans a 30-year period with
about 23 years of drought and seven years of wet
conditions. Because the most recent wet period (1993-
2000) ended three years ago, reservoir water levels
should continue to decline over the next 20 years.
However, even if these long-term predictions are
correct, the impacts of recent high water have been
severe. Tree mortality has been significant,
regeneration of the woody component is sparse, and
non-native vegetation has replaced natives in the
understory. Undoubtedly, such changes have also
altered the avian community from what was reported
in the mid-1990’s. Perhaps more important,
restoration will be costly in terms of both money and
labor. Some of the dead timber may have to be
removed, the invasive species controlled, and suitable
conditions for regeneration of desirable trees and
grasses created. Therefore, it is recommended that
more information be obtained regarding the
relationship between reservoir pool elevations and the
duration and depth of floodplain inundation for
different reaches of the riparian community. This
would help in determining the potential costs,
benefits, and reliability of managing different portions
of the riparian community. Several techniques could
be used to develop information on flooding depth in the
floodplain. The most comprehensive (e.g., full range
of estimates) and accurate technique would involve the
use of bathymetry or topographic data that
encompasses both the reservoir and tributary
streams. Alternatively, current aerial photographs of
the reservoir at different pool elevations could be used
to estimate relationships. Data on flood frequency
and duration can be developed based on the number of
times and duration the reservoir pool exceeded certain
elevations, respectively.
Management Potential – Streams, and their
associated floodplains, are complex ecological systems
that provide many benefits to society. Throughout the
western United States, these areas are valued as a
source of water, recreational activities, and the unique
plant and wildlife resources they support. Due to
these myriad values, they also are among the most
highly modified systems. Usually a single stream is
owned and managed by multiple entities for purposes
that often conflict to some extent. Thus, the ability to
successfully manage a reach for a specific outcome is
often influenced by uses both upstream and
downstream of the site.
Although the above description is generic and applies
to many streams, it aptly describes the portions of the
North Fork Solomon River and Bow Creek managed
by FWS. The values of this community are still
apparent based on available data. However, past
alterations both upstream and downstream of the
refuge have caused significant changes that affect the
ability of FWS to maintain the functions and processes
that supported the historic riparian community. Of
primary concern are the hydrologic alterations that
result in extreme water level fluctuations in the
floodplain. High water similar to that experienced in
the mid-1990’s may occur infrequently, but the cost of
restoring the native community following such events
19
likely will be time-consuming and costly. Further, this
effort may be required every 20-30 years based on
long-term predictions. Potential solutions that
address the entire riparian community are not readily
apparent because release of water from the reservoir
during high flow periods would be required. This is
not likely since a primary reason for reservoir
construction was to store this water for irrigation
below Kirwin. If a viable solution is not found, it is
recommended that the benefits and costs associated
with managing different portions of the riparian
community be evaluated. This may result in the
identification of portions that are relatively free of
reservoir impacts. Part of this analysis would require
determining the likelihood that certain reservoir
elevations will occur during a given time period and
estimating the riparian area impacted at these
elevations. For example, a reservoir elevation of 528.8
m (1735.0 ft) would likely occur 2 times every 20 years.
At this elevation, 20% of the riparian community
would be flooded to depths that cause significant
damage. Based on these probabilities, the riparian
community could be divided into areas that are
frequently and infrequently prone to reservoir
impacts. Each of these areas could be addressed
differently. For example, the area not prone to
reservoir impacts could be managed to provide the full
range of floristic composition and structure desired
with a high level of probability that progress would
not be impacted by the reservoir. In contrast,
management effort in the area frequently
experiencing reservoir impacts would differ because
the benefits would be short-term and the cost
excessive. This does not mean that this portion of the
riparian community would be abandoned; rather a
different set of management goals would be developed
that take into account uncontrollable factors.
Upland
Kirwin NWR is within the central dissected, or mixed-grass,
prairie region that historically was dominated
by the bluestem-grama association (Launchbaugh and
Owensby 1978). This association was prevalent on
uplands in west-central Kansas, but also extended
west on breaks into the dissected parts of the High
Plains where the grama-buffalo grass prairie
dominated the landscape. According to Kuchler
(1974), the bluestem-grama association is
characterized by dense communities of grasses and
forbs that often are in two distinct layers: one of low-growing
grasses and one of medium tall grasses and
forbs that is usually more open. Dominant species are
big and little bluestem, sideoats grama, and blue
grama. Other characteristic species include western
wheatgrass, western ragweed, leadplant, purple
threeawn, hairy grama, buffalo grass, Freemont’s
clematis, purple coneflower, and Canada wildrye
among others.
Factors historically controlling the distribution and
physiognomy of the mixed-grass prairie included
precipitation, fire, and herbivory. The plant species
composing this prairie are sensitive to major
precipitation fluctuations; thus, their distribution
tends to move east and west in response to alternating
periods of intense drought or wetness (Kuchler 1967,
1972). Summer fires (Sauer 1950) and herbivory
(Dyksterhuis 1958) also helped maintain the prairie by
suppressing woody vegetation. However, certain
woody plants were always present as natural
components in some areas (Kuchler 1974).
Herbivores, including bison and smaller vertebrates
such as prairie dogs, altered soil characteristics and
other factors that influenced plant establishment and
growth (Kuchler 1974).
Following the onset of human settlement, however,
processes were modified that profoundly affected the
prairie (Knopf and Samson 1997). Fire suppression,
development and expansion of agricultural crops,
changes in herbivores and herbivory, and planting of
trees have significantly altered the prairie landscape.
In addition, technological advances brought about
other less obvious but equally important changes,
including the development and introduction of new
grasses and crops, groundwater pumping, herbicides,
and fertilization. These and other actions have
resulted in significant loss and fragmentation of the
prairie community. For example, currently about 60%
of Kansas lands are used for agriculture. Of this 60%,
about 48% is cropland and the other 12% is non-native
grasses (e.g., brome) or CRP (seeded natives).
The condition on Kirwin NWR is representative of the
conditions for Kansas as a whole. The refuge
encompasses about 2,833 ha (7,000 ac) of uplands at
conservation pool and 2,712 ha (6,700 ac) at a pool
elevation of 527.7 m (1,731.3 ft). Grasslands dominate
this acreage, but the refuge staff reports that only
about 81 ha (200 ac) of native grass occur on the
refuge. The remainder is either pasture or reseeded
grass. Further, much of the native grass is isolated
(i.e., fragmented) and occurs in small blocks. Other
habitats occurring in the uplands include shelterbelts,
croplands, chalk bluffs, and a few temporary
wetlands. Although the exact area of shelterbelts is
not known, many appear to be 15-31 m (50-100 ft) wide
and extend for various distances along roads and fence
lines. The tree composition includes a mix of both
hardwood and evergreen species. Wheat, sorghum,
corn, and alfalfa are the dominant crops on the refuge
and approximately 486 ha (1,200 ac) are planted
annually when the reservoir is at an elevation of 527.1
m (1729.25 ft). The cropping program is designed to
prepare agricultural land for conversion to grass and
provide foods for migratory birds and resident
wildlife. Farming is accomplished using cooperative
farmers and arrangements vary depending on crop
(refuge staff). For example, the refuge share of row
crops is 25%, whereas stubble constitutes the refuge
share of wheat.
Chalk outcroppings occur at higher elevations in the
uplands, whereas only a few palustrine wetlands occur
in depressional areas. Both of these communities
exist as small, disjunct areas that compose only a
small percentage of refuge lands. Although not
covered in this report due to lack of information, both
support some distinctive plant species and constitute
unique habitats on the refuge. Thus, additional
information should be obtained regarding their
locations, sizes, and unique resources.
20
Most of the remaining discussion uses the grassland
component of the uplands as the baseline condition.
This approach was used because comparing and
contrasting the values and management options of
multiple plant communities without a standard for
comparison is confusing. Grassland was selected as
the standard because it represents the historic plant
community and presently dominates the uplands.
Also, the values and methods of managing other
habitats (e.g., corn, shelterbelts) in the uplands are
largely known and require little discussion.
Although much of the historic prairie on the refuge
was converted or degraded prior to establishment,
this community (excluding areas adjacent to the
reservoir) appears to be the least effected by the
reservoir. Consequently, FWS has more direct
control and can likely influence future conditions
more reliably. In general, the current condition of
refuge grasslands varies greatly. There are small
areas, many on the south side of the reservoir, that
contain a high proportion of native grass and forb
species. In contrast, other areas are primarily
composed of non-native, cool season grasses. The
dominant non-native species is smooth brome, but
small areas of Kentucky bluegrass also are present
(refuge staff). Finally, areas in various stages of
restoration also occur on the refuge. Species
composition of these stands is mixed, with the
presence of both warm season natives and cool season
non-natives. Unfortunately, more detailed information
on the current condition of the grasslands is lacking.
Maps depicting the locations and sizes of different
grassland types (native, reseeded, tame) are not
available, and both qualitative and quantitative
information regarding the floristic composition
(species of grasses, forbs) and structure of each type
are unknown. Although all information is rarely
available, the lack of at least some of the above
information renders any comments incomplete and
speculative. Therefore, the following information is
provided as a recommendation regarding the types of
information that should be developed prior to CCP
development. In addition, examples are provided
regarding potential uses of this information for
developing future management direction.
First, the locations and floristic composition of the
different grassland types should be determined. The
most proficient method would be to develop a digital
vegetation map based on floristics rather than generic
terms such as pasture, reseeded grass, or native
grass. The latter terms can be misleading if labels
are not applied based on floristic attributes and often
do not convey sufficient information to determine
current value or management options. For example,
the designation of native grass on the refuge appears
to be based on the premise that the ground has never
been plowed (e.g., unbroken sod is another frequently
used term). Such a designation may be correct and
provide some information, but definitions based solely
on past management actions (or lack thereof) do not
guarantee that floristic composition and/or structure
are representative of the historic native community.
For example, invasive grasses (e.g., smooth brome)
can invade areas never plowed and alter plant and bird
community composition and structure (Wilson and
Belcher 1989). Therefore, there is also no guarantee
that the plant community will provide suitable habitat
for vertebrates (e.g., birds) and invertebrates (e.g.,
butterflies) that are an important part of the
grassland community.
Second, the current value of the different grassland
communities identified during vegetation mapping
must be determined. Many vertebrates and
invertebrates exhibit plasticity and can tolerate
certain changes in plant composition and/or structure.
Thus, certain non-native communities, or mixed
native/non-native communities, may provide sufficient
value to warrant maintaining on the refuge. For
example, row crops and wheat provide foods for select
species of waterfowl, shelterbelts provide suitable
habitat for certain songbirds, and CRP plantings that
often include some non-native species provide benefits
to some grassland birds. The benefits provided by
these habitats must be compared to the potential
benefits that would result from converting portions of
these areas to other types. For example, shelterbelts
provide habitat for some songbirds, but represent
“hostile environments” that can hinder breeding by
some grassland bird species. Thus, removing
shelterbelts to increase the contiguous area of
grasslands above a threshold size may benefit
grassland birds but negatively impact songbird
numbers. Such tradeoffs should be documented prior
to making management decisions. Part of this
analysis should also involve evaluating the spatial
attributes (e.g., size, location) of each community.
Appropriate floristic composition and structure is
important, but many species also require areas of
certain size, or multiple communities in close
juxtaposition, to adequately meet life history
requisites (Herkert 1994, Helzer and Jelinski 1999,
Walk and Warner 1999). For example, some species of
grassland birds known to occur on the refuge exhibit
minimum area requirements for nesting. Therefore,
the grassland areas that have been developed for
public use may not constitute suitable habitat because
the extensive road network may have fragmented
these areas sufficiently, regardless of human activities
associated with these areas.
Although a large amount of information exists on
species-habitat relationships, attempts often are made
to assess values based on opinions and past
experiences. This often results in confusion and
conflict. Therefore, it is recommended that objective
information be developed prior to discussing the
relative merits of each community. This may seem
daunting, but much of the information on bird-habitat
relationships has already been compiled for many
species known to occur on the refuge, and additional
research could be conducted. The digital vegetation
map also would prove invaluable because it could be
used to assess size of each community or distances
between communities.
Third, the benefits and detriments of altering the
type, size, or spatial location of various communities
should be evaluated. For example, the removal of
shelterbelts and/or cropland in certain areas may not
21
result in the creation of contiguous grassland that
exceeds a threshold required to meet the needs of
certain avian species. In such cases, the costs of
conversion would not be warranted because it would
not result in expected benefits. Similarly, the public
use facilities may fragment grasslands in the eastern
portion of the refuge sufficiently to preclude nesting
by some wildlife. If this were true, the benefits of
managing these areas to provide specific structural
conditions may not be worth the cost. If a digital
vegetation map were available, various scenarios could
be portrayed graphically to determine the best
configuration and size of different community types.
Finally, information should be developed to evaluate
the potential of accomplishing different activities. For
example, statements made by the refuge staff suggest
that the current conditions of most existing
grasslands are not desirable. If an evaluation
confirms this statement, then decisions must be made
regarding the potential for different grassland areas.
An initial step could involve classifying each grassland
tract as being in need of either restoration or
maintenance. This is an important distinction because
maintenance implies that the existing floristic
composition is acceptable and management is directed
toward altering structural components (e.g., litter
depth, height, density). Although not everything is
known, the use of tools (fire, herbivory, mowing) to
maintain grasslands has received considerable
attention by the scientific community and general
concepts exist regarding appropriate techniques. In
contrast, true “prairie” restoration is much more
difficult. A review of the literature suggests some
techniques have reliably proven successful in
establishing some components of prairie (e.g., warm
season grass), but much remains to be learned
regarding restoration of all components (e.g., forbs,
native cool season grasses). This is particularly true
of mixed-grass prairie. Little definitive information
exists that provides guidance in determining
appropriate site preparation, seed mixtures, or time
and rate of seeding for different components relative
to specific site conditions (e.g., soil type, groundwater
table).
The lack of information for the existing grassland
communities, in combination with the lack of proven
restoration techniques for mixed-grass prairie,
suggests that attempts to convert existing upland
communities to native prairie will be difficult.
However, this does not mean that an attempt should
not be made. Rather, it indicates that success will
require much work over numerous years (Kindscher
and Tieszen 1998, Fuhlendorf et al. 2002), development
of appropriate monitoring techniques, and frequent
experimentation. An extensive search of the
literature and consultations with local experts likely
will provide initial guidance useful for identifying
potential attributes that may influence restoration
potential. This information could then be used to
refine additional searches for refuge-specific
information on these attributes. For example, if
depths to groundwater or certain soil characteristics
are deemed important, this information could be
obtained from various sources and evaluated to
determine the most likely locations to attempt
restoration.
Management Potential – In many respects, FWS can
exert the greatest influence on the upland community
compared to other community types. However,
constraints still exist that will influence future
conditions. Uplands adjacent to the reservoir are
wetter during high water years and extensive
groundwater pumping upstream of the refuge likely
has altered the subsurface hydrology of some upland
habitats. The effects of these alterations are
unknown, but research indicates change in the water
table can effectively alter environmental conditions
and, therefore, plant species occurrence (Currier
1988). Thus, literature reviews should be conducted
to determine potential changes in abiotic conditions
that would preclude certain management options. For
example, restoration of native grasses and forbs
adjacent to the reservoir may not be feasible due to
changes in soil characteristics. If this is the case,
another grassland type or habitat should be
considered. In addition, invasive species have altered
floristic and structural attributes of many grassland
tracts. Although techniques have been developed for
controlling many of these species, desirable
vegetation must be established following control or
there are no long-term biological benefits. The ability
to accomplish this task largely will depend on what is
considered a desirable community. Depending on the
types of natural resource benefits the core team
decides the refuge should provide, grasslands ranging
from native mixed-grass prairie to CRP or tame
grasses may be appropriate. Some of these types can
be developed with a high degree of certainty, whereas
others are very difficult to establish and maintain.
Finally, some plant communities (e.g., shelterbelts,
croplands) and the public use facilities were not
present historically. Although such features may be
considered obstructions from the perspective of
historic conditions, they provide values that cannot,
and should not, be ignored. Therefore, decisions must
be made regarding the appropriate mix of historic and
current conditions. These decisions will likely
influence the types and configuration of the different
communities composing the uplands.
22
Public Use
In addition to wildlife benefits, the refuge provides
various forms of public recreation that should be
mentioned. At conservation pool there are 1,402 ha
(3,465 ac) of surface water (68.4% of reservoir) open to
activities such as boat fishing, water skiing and jet
skiing. In addition, about 41 ha (100 ac) of grassland
adjacent to the main body of the reservoir are
developed for public use, including shore fishing,
camping, and picnicking (U. S. Bureau of Reclamation,
URL http://www.usbr.gov/gp). There is also an
extensive road network, including a tour loop around
the perimeter of the refuge. Finally, hunting (deer
and waterfowl primarily) is allowed in both the
riparian and upland communities. Given the number
and types of recreational visits to the refuge (U.S.
Bureau of Reclamation 2002), it is possible that human
activities could represent a disturbance that impacts
some species that use the refuge. Peak waterfowl and
shorebird migration periods do not appear to coincide
with peak recreational periods (refuge staff).
However, ground nesting ducks (e.g., Gadwall,
Mallard), Least Terns, grassland birds, and species
that nest in trees adjacent to deepwater habitat (e.g.,
Double-crested Cormorants, Great Blue Herons, and
Bald Eagles) are present during the summer
recreational period. Various regional and national
plans consider populations of some of these species to
be of concern (Appendix D) and information is
available that indicates human activities can interfere
with the successful rearing of young of these species.
Despite these observations, which only allude to
possibilities, there is not sufficient evidence to either
confirm or discount conflicts. However, the fact that
human-wildlife conflicts may occur identifies the need
to develop specific information regarding potential
detrimental impacts to wildlife. Scientific information
addressing the effects of disturbance is available, but
conditions on Kirwin NWR may differ from those
reported elsewhere. Thus, definitive resolution of this
concern may require conducting an appropriately
designed monitoring program or research study on
the refuge. Regardless of the source, this information
could be used to develop solutions that eliminate or
minimize impacts without negatively impacting public
use opportunities.
Finally, the refuge staff has responsibility for
enforcing regulations and maintaining facilities
associated with recreational activities. Currently, the
staff estimate that possibly 50 to 60% of their time is
annually devoted to tasks associated with the public
use program (refuge staff). This amount of effort,
although often warranted, should be evaluated relative
to the time required to achieve the biological goals
established in the CCP. FWS should use this
evaluation to determine an appropriate balance
between natural resource and public use
management, and adjust budgetary and time
requirements to meet these needs.
23
Literature Cited
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American Ornithologists’ Union. 1998. Check-list of North American Birds. 7th edition. American
Ornithologists’ Union, Washington, D.C.
American Ornithologists’ Union. 2000. Forty-second supplement to the American Ornithologists’ Union Check-list
of North American Birds. Auk 117:847-858.
American Ornithologists’ Union. 2002. Forty-third supplement to the American Ornithologists’ Union Check-list
of North American Birds. Auk 119:897-906.
American Ornithologists’ Union. 2003. Forty-fourth supplement to the American Ornithologists’ Union Check-list
of North American Birds. Auk 120:923-931.
Bailey, J. K., J. A. Schweitzer, and T. G. Whitman. 2001. Saltcedar negatively affects biodiversity of aquatic
macroinvertebrates. Wetlands 21:442-447.
Baker, L. A. 1992. Introduction to nonpoint source pollution in the United States and prospects for wetland use.
Ecological Engineering 1:1-26.
Callender, E., and J. A. Robbins. 1993. Transport and accumulation of radionuclides in stable elements in a
Missouri River system. Water Resources Research 29:1787-1804.
Carothers, S. W., R. R. Johnson, and S. W Aitchison. 1974. Population structure and social organization of
southwestern riparian birds. American Zoologist 14:97-108.
Christensen, V. G. 1999. Deposition of selenium and other constituents in reservoir bottom sediment of the
Solomon River Basin, north-central Kansas. U.S. Geological Survey, Water Resources Investigations Report 99-
4230.
Christensen, V. G., and K. E. Juracek. 2001. Variability of metals in reservoir sediment from two adjacent basins
in the central Great Plains. Environmental Geology 40:470-481.
Currier, P. J. 1988. Plant species composition and groundwater levels in a Platte River wet meadow. Pages 19-24
in T. B. Bragg and J. Stubbendieck, editors. Proceedings of the 11th North American Prairie Conference.
University of Nebraska, Lin